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<a href="pool__arena_8hpp.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a id="l00001" name="l00001"></a><span class="lineno">    1</span><span class="comment">/* Flow-IPC: Shared Memory</span></div>
<div class="line"><a id="l00002" name="l00002"></a><span class="lineno">    2</span><span class="comment"> * Copyright 2023 Akamai Technologies, Inc.</span></div>
<div class="line"><a id="l00003" name="l00003"></a><span class="lineno">    3</span><span class="comment"> *</span></div>
<div class="line"><a id="l00004" name="l00004"></a><span class="lineno">    4</span><span class="comment"> * Licensed under the Apache License, Version 2.0 (the</span></div>
<div class="line"><a id="l00005" name="l00005"></a><span class="lineno">    5</span><span class="comment"> * &quot;License&quot;); you may not use this file except in</span></div>
<div class="line"><a id="l00006" name="l00006"></a><span class="lineno">    6</span><span class="comment"> * compliance with the License.  You may obtain a copy</span></div>
<div class="line"><a id="l00007" name="l00007"></a><span class="lineno">    7</span><span class="comment"> * of the License at</span></div>
<div class="line"><a id="l00008" name="l00008"></a><span class="lineno">    8</span><span class="comment"> *</span></div>
<div class="line"><a id="l00009" name="l00009"></a><span class="lineno">    9</span><span class="comment"> *   https://www.apache.org/licenses/LICENSE-2.0</span></div>
<div class="line"><a id="l00010" name="l00010"></a><span class="lineno">   10</span><span class="comment"> *</span></div>
<div class="line"><a id="l00011" name="l00011"></a><span class="lineno">   11</span><span class="comment"> * Unless required by applicable law or agreed to in</span></div>
<div class="line"><a id="l00012" name="l00012"></a><span class="lineno">   12</span><span class="comment"> * writing, software distributed under the License is</span></div>
<div class="line"><a id="l00013" name="l00013"></a><span class="lineno">   13</span><span class="comment"> * distributed on an &quot;AS IS&quot; BASIS, WITHOUT WARRANTIES OR</span></div>
<div class="line"><a id="l00014" name="l00014"></a><span class="lineno">   14</span><span class="comment"> * CONDITIONS OF ANY KIND, either express or implied.</span></div>
<div class="line"><a id="l00015" name="l00015"></a><span class="lineno">   15</span><span class="comment"> * See the License for the specific language governing</span></div>
<div class="line"><a id="l00016" name="l00016"></a><span class="lineno">   16</span><span class="comment"> * permissions and limitations under the License. */</span></div>
<div class="line"><a id="l00017" name="l00017"></a><span class="lineno">   17</span><span class="comment"></span> </div>
<div class="line"><a id="l00018" name="l00018"></a><span class="lineno">   18</span><span class="comment">/// @file</span></div>
<div class="line"><a id="l00019" name="l00019"></a><span class="lineno">   19</span><span class="comment"></span><span class="preprocessor">#pragma once</span></div>
<div class="line"><a id="l00020" name="l00020"></a><span class="lineno">   20</span> </div>
<div class="line"><a id="l00021" name="l00021"></a><span class="lineno">   21</span><span class="preprocessor">#include &quot;<a class="code" href="shm_2classic_2classic__fwd_8hpp.html">ipc/shm/classic/classic_fwd.hpp</a>&quot;</span></div>
<div class="line"><a id="l00022" name="l00022"></a><span class="lineno">   22</span><span class="preprocessor">#include &quot;<a class="code" href="arena__activator_8hpp.html">ipc/shm/stl/arena_activator.hpp</a>&quot;</span></div>
<div class="line"><a id="l00023" name="l00023"></a><span class="lineno">   23</span><span class="preprocessor">#include &quot;<a class="code" href="shared__name_8hpp.html">ipc/util/shared_name.hpp</a>&quot;</span></div>
<div class="line"><a id="l00024" name="l00024"></a><span class="lineno">   24</span><span class="preprocessor">#include &quot;<a class="code" href="util_8hpp.html">ipc/util/detail/util.hpp</a>&quot;</span></div>
<div class="line"><a id="l00025" name="l00025"></a><span class="lineno">   25</span><span class="preprocessor">#include &lt;flow/util/basic_blob.hpp&gt;</span></div>
<div class="line"><a id="l00026" name="l00026"></a><span class="lineno">   26</span><span class="preprocessor">#include &lt;boost/interprocess/managed_shared_memory.hpp&gt;</span></div>
<div class="line"><a id="l00027" name="l00027"></a><span class="lineno">   27</span><span class="preprocessor">#include &lt;boost/interprocess/indexes/null_index.hpp&gt;</span></div>
<div class="line"><a id="l00028" name="l00028"></a><span class="lineno">   28</span><span class="preprocessor">#include &lt;optional&gt;</span></div>
<div class="line"><a id="l00029" name="l00029"></a><span class="lineno">   29</span> </div>
<div class="line"><a id="l00030" name="l00030"></a><span class="lineno">   30</span><span class="keyword">namespace </span><a class="code hl_namespace" href="namespaceipc_1_1shm_1_1classic.html">ipc::shm::classic</a></div>
<div class="line"><a id="l00031" name="l00031"></a><span class="lineno">   31</span>{</div>
<div class="line"><a id="l00032" name="l00032"></a><span class="lineno">   32</span> </div>
<div class="line"><a id="l00033" name="l00033"></a><span class="lineno">   33</span><span class="comment">// Types.</span></div>
<div class="line"><a id="l00034" name="l00034"></a><span class="lineno">   34</span><span class="comment"></span> </div>
<div class="line"><a id="l00035" name="l00035"></a><span class="lineno">   35</span><span class="comment">/**</span></div>
<div class="line"><a id="l00036" name="l00036"></a><span class="lineno">   36</span><span class="comment"> * A SHM-classic interface around a single SHM pool with allocation-algorithm services by boost.interprocess,</span></div>
<div class="line"><a id="l00037" name="l00037"></a><span class="lineno">   37</span><span class="comment"> * as in `bipc::managed_shared_memory`, with symmetric read/write semantics, compatible with ipc::shm::stl</span></div>
<div class="line"><a id="l00038" name="l00038"></a><span class="lineno">   38</span><span class="comment"> * STL-compliance and SHM-handle borrowing manually or via ipc::session.</span></div>
<div class="line"><a id="l00039" name="l00039"></a><span class="lineno">   39</span><span class="comment"> *</span></div>
<div class="line"><a id="l00040" name="l00040"></a><span class="lineno">   40</span><span class="comment"> * ### When to use ###</span></div>
<div class="line"><a id="l00041" name="l00041"></a><span class="lineno">   41</span><span class="comment"> * Generally, this is a simple way to work with SHM.  It is very easy to set up and has very little infrastructure</span></div>
<div class="line"><a id="l00042" name="l00042"></a><span class="lineno">   42</span><span class="comment"> * on top of what is provided by a typically-used subset of bipc&#39;s SHM API -- which, itself, is essentially a thin</span></div>
<div class="line"><a id="l00043" name="l00043"></a><span class="lineno">   43</span><span class="comment"> * wrapper around a classic OS-supplied SHM pool (segment) API, plus a Boost-supplied heap-like allocation algorithm.</span></div>
<div class="line"><a id="l00044" name="l00044"></a><span class="lineno">   44</span><span class="comment"> * Nevertheless this wrapper, when combined with ipc::shm::stl, is eminently usable and flexible.  Its main</span></div>
<div class="line"><a id="l00045" name="l00045"></a><span class="lineno">   45</span><span class="comment"> * limitations may or may not be serious in production use, depending on the context.  These limitations include</span></div>
<div class="line"><a id="l00046" name="l00046"></a><span class="lineno">   46</span><span class="comment"> * the following.</span></div>
<div class="line"><a id="l00047" name="l00047"></a><span class="lineno">   47</span><span class="comment"> *   - When buffers are allocated and deallocated, bipc&#39;s default memory allocation algorithm -- `rbtree_best_fit` --</span></div>
<div class="line"><a id="l00048" name="l00048"></a><span class="lineno">   48</span><span class="comment"> *     is what is used.  (We could also allow for the other supplied algo, `simple_seq_fit`, or a custom</span></div>
<div class="line"><a id="l00049" name="l00049"></a><span class="lineno">   49</span><span class="comment"> *     user-supplied one.)  While surely care was taken in writing this, in production one might demand</span></div>
<div class="line"><a id="l00050" name="l00050"></a><span class="lineno">   50</span><span class="comment"> *     something with thread caching and just general, like, industry relevance/experience; a jemalloc or</span></div>
<div class="line"><a id="l00051" name="l00051"></a><span class="lineno">   51</span><span class="comment"> *     tcmalloc maybe.</span></div>
<div class="line"><a id="l00052" name="l00052"></a><span class="lineno">   52</span><span class="comment"> *     - Possible contingency: Not really.  In many cases this does not matter too much; but if one wants general</span></div>
<div class="line"><a id="l00053" name="l00053"></a><span class="lineno">   53</span><span class="comment"> *       performance equal to that of the general heap in a loaded production environment, then classic::Pool_arena</span></div>
<div class="line"><a id="l00054" name="l00054"></a><span class="lineno">   54</span><span class="comment"> *       is probably not for you.  Consider jemalloc-based SHM provided elsewhere in ipc::shm.</span></div>
<div class="line"><a id="l00055" name="l00055"></a><span class="lineno">   55</span><span class="comment"> *   - It works within exactly one *pool* a/k/a `mmap()`ped segment, and that pool&#39;s max size must be specified</span></div>
<div class="line"><a id="l00056" name="l00056"></a><span class="lineno">   56</span><span class="comment"> *     at creation.  Once it is exhausted via un-deallocated allocations, it&#39;ll throw exceptions likely to wreak</span></div>
<div class="line"><a id="l00057" name="l00057"></a><span class="lineno">   57</span><span class="comment"> *     havoc in your application.</span></div>
<div class="line"><a id="l00058" name="l00058"></a><span class="lineno">   58</span><span class="comment"> *     - Possible contingency: You may set the max pool size to a giant value.  This will *not* take it from</span></div>
<div class="line"><a id="l00059" name="l00059"></a><span class="lineno">   59</span><span class="comment"> *       the OS like Linux: only when a page is actually touched, such as by allocating in it, does that actual</span></div>
<div class="line"><a id="l00060" name="l00060"></a><span class="lineno">   60</span><span class="comment"> *       RAM get assigned to your application(s).  There is unfortunately, at least in Linux, some configurable</span></div>
<div class="line"><a id="l00061" name="l00061"></a><span class="lineno">   61</span><span class="comment"> *       kernel parameters as to the sum of max pool sizes active at a given time -- `ENOSPC` (No space left on device)</span></div>
<div class="line"><a id="l00062" name="l00062"></a><span class="lineno">   62</span><span class="comment"> *       may be emitted when trying to open a pool beyond this.  All in all it is a viable approach but may need</span></div>
<div class="line"><a id="l00063" name="l00063"></a><span class="lineno">   63</span><span class="comment"> *       a measure of finesse.</span></div>
<div class="line"><a id="l00064" name="l00064"></a><span class="lineno">   64</span><span class="comment"> *   - The ability to allocate in a given backing pool via any process&#39;s Pool_arena handle to that</span></div>
<div class="line"><a id="l00065" name="l00065"></a><span class="lineno">   65</span><span class="comment"> *     backing pool -- not to mention deallocate in process B what was allocated in process A -- requires</span></div>
<div class="line"><a id="l00066" name="l00066"></a><span class="lineno">   66</span><span class="comment"> *     guaranteed read-write capability in all `Pool_arena`s accessing a given pool.  That read-write capability</span></div>
<div class="line"><a id="l00067" name="l00067"></a><span class="lineno">   67</span><span class="comment"> *     in and of itself (orthogonally to allocations) provides algorithmic possibilities which are not</span></div>
<div class="line"><a id="l00068" name="l00068"></a><span class="lineno">   68</span><span class="comment"> *     easily available in an asymmetric setup, where only one process can write or deallocate, while others</span></div>
<div class="line"><a id="l00069" name="l00069"></a><span class="lineno">   69</span><span class="comment"> *     can only borrow handles and read.  How is this a limitation, you ask?  While providing power and</span></div>
<div class="line"><a id="l00070" name="l00070"></a><span class="lineno">   70</span><span class="comment"> *     simplicity, it also hugely increases the number and difficulty of dealing with unexpected conditions.</span></div>
<div class="line"><a id="l00071" name="l00071"></a><span class="lineno">   71</span><span class="comment"> *     That is -- any process can write and corrupt the pool&#39;s contents, thus &quot;poisoning&quot; other processes;</span></div>
<div class="line"><a id="l00072" name="l00072"></a><span class="lineno">   72</span><span class="comment"> *     any process crashing means the others cannot trust the integrity of the pool&#39;s contents; things of that</span></div>
<div class="line"><a id="l00073" name="l00073"></a><span class="lineno">   73</span><span class="comment"> *     nature.</span></div>
<div class="line"><a id="l00074" name="l00074"></a><span class="lineno">   74</span><span class="comment"> *     - Possible contingency: It would not be difficult to enable read-only access from all but one process;</span></div>
<div class="line"><a id="l00075" name="l00075"></a><span class="lineno">   75</span><span class="comment"> *       we provide such a constructor argument.  However, one cannot use the SHM-handle borrowing method</span></div>
<div class="line"><a id="l00076" name="l00076"></a><span class="lineno">   76</span><span class="comment"> *       borrow_object() which severely stunts the usefulness of the class in that process and therefore across</span></div>
<div class="line"><a id="l00077" name="l00077"></a><span class="lineno">   77</span><span class="comment"> *       the system.  That said one could imagine somewhat extending Pool_arena to enable lend-borrow and</span></div>
<div class="line"><a id="l00078" name="l00078"></a><span class="lineno">   78</span><span class="comment"> *       delegated deallocation (and maybe delegated allocation while at it) by adding some internal</span></div>
<div class="line"><a id="l00079" name="l00079"></a><span class="lineno">   79</span><span class="comment"> *       message-passing (maybe through a supplied transport::Channel or something).  Doable but frankly</span></div>
<div class="line"><a id="l00080" name="l00080"></a><span class="lineno">   80</span><span class="comment"> *       goes against the spirit of simplicty and closeness-to-the-&quot;source-material&quot; cultivated by</span></div>
<div class="line"><a id="l00081" name="l00081"></a><span class="lineno">   81</span><span class="comment"> *       classic::Pool_arena.  The jemalloc-based API available elsewhere in ipc::shm is the one that</span></div>
<div class="line"><a id="l00082" name="l00082"></a><span class="lineno">   82</span><span class="comment"> *       happily performs message-passing IPC internally for such reasons.  It&#39;s a thought though.</span></div>
<div class="line"><a id="l00083" name="l00083"></a><span class="lineno">   83</span><span class="comment"> *</span></div>
<div class="line"><a id="l00084" name="l00084"></a><span class="lineno">   84</span><span class="comment"> * ### Properties ###</span></div>
<div class="line"><a id="l00085" name="l00085"></a><span class="lineno">   85</span><span class="comment"> * Backing pool structure: One (1) SHM pool, explicitly named at construction.  Can open handle with create-only,</span></div>
<div class="line"><a id="l00086" name="l00086"></a><span class="lineno">   86</span><span class="comment"> * create-or-open (atomic), or open-only semantics.  Pool size specified at construction/cannot be changed.</span></div>
<div class="line"><a id="l00087" name="l00087"></a><span class="lineno">   87</span><span class="comment"> * Vaddr structure is not synchronized (so `void* p` pointing into SHM in process 1 cannot be used in process 2</span></div>
<div class="line"><a id="l00088" name="l00088"></a><span class="lineno">   88</span><span class="comment"> * without first adjusting it based on the different base vaddr of the mapped pool in process 2 versus 1).</span></div>
<div class="line"><a id="l00089" name="l00089"></a><span class="lineno">   89</span><span class="comment"> *</span></div>
<div class="line"><a id="l00090" name="l00090"></a><span class="lineno">   90</span><span class="comment"> * Handle-to-arena structure: Pool_arena is the only type, used by any process involved, that accesses the underlying</span></div>
<div class="line"><a id="l00091" name="l00091"></a><span class="lineno">   91</span><span class="comment"> * arena, and once open all capabilities are symmetrically available to all Pool_arena objects in all processes.</span></div>
<div class="line"><a id="l00092" name="l00092"></a><span class="lineno">   92</span><span class="comment"> *   - Any `Pool_arena` can allocate (and deallocate what it has allocated).</span></div>
<div class="line"><a id="l00093" name="l00093"></a><span class="lineno">   93</span><span class="comment"> *   - Any `Pool_arena` can deallocate what any other `Pool_arena` has allocated (as long as the correct</span></div>
<div class="line"><a id="l00094" name="l00094"></a><span class="lineno">   94</span><span class="comment"> *     locally-dereferenceable `void*` has been obtained in the deallocating process).</span></div>
<div class="line"><a id="l00095" name="l00095"></a><span class="lineno">   95</span><span class="comment"> *</span></div>
<div class="line"><a id="l00096" name="l00096"></a><span class="lineno">   96</span><span class="comment"> * Allocation algorithm: As of this writing the bipc default, `rbtree_best_fit`.  See its description in bipc docs.</span></div>
<div class="line"><a id="l00097" name="l00097"></a><span class="lineno">   97</span><span class="comment"> * Note it does not perform any thread-caching like modern `malloc()`s.</span></div>
<div class="line"><a id="l00098" name="l00098"></a><span class="lineno">   98</span><span class="comment"> *</span></div>
<div class="line"><a id="l00099" name="l00099"></a><span class="lineno">   99</span><span class="comment"> * Allocation/deallocation API: See section below for proper use techniques.</span></div>
<div class="line"><a id="l00100" name="l00100"></a><span class="lineno">  100</span><span class="comment"> *</span></div>
<div class="line"><a id="l00101" name="l00101"></a><span class="lineno">  101</span><span class="comment"> * Cleanup: The underlying SHM pool is deleted if and only if one calls remove_persistent(), supplying it the</span></div>
<div class="line"><a id="l00102" name="l00102"></a><span class="lineno">  102</span><span class="comment"> * pool name.  This is not invoked internally at all, so it is the user&#39;s responsibility.  ipc::session-managed</span></div>
<div class="line"><a id="l00103" name="l00103"></a><span class="lineno">  103</span><span class="comment"> * `Pool_arena`s will be automatically cleaned up, as ipc::session strives to clean all persistent shared</span></div>
<div class="line"><a id="l00104" name="l00104"></a><span class="lineno">  104</span><span class="comment"> * resources via a general algorithm.  See remove_persistent() and for_each_persistent() doc headers.</span></div>
<div class="line"><a id="l00105" name="l00105"></a><span class="lineno">  105</span><span class="comment"> *</span></div>
<div class="line"><a id="l00106" name="l00106"></a><span class="lineno">  106</span><span class="comment"> * Satisfies `Arena` requirements for shm::stl::Stateless_allocator: Yes.  I.e., it is easy to store</span></div>
<div class="line"><a id="l00107" name="l00107"></a><span class="lineno">  107</span><span class="comment"> * STL-compliant containers directly in SHM by using `Stateless_allocator&lt;Pool_arena&gt;` as the allocator at all</span></div>
<div class="line"><a id="l00108" name="l00108"></a><span class="lineno">  108</span><span class="comment"> * levels.</span></div>
<div class="line"><a id="l00109" name="l00109"></a><span class="lineno">  109</span><span class="comment"> *   - SHM-stored pointer type provided: Yes, #Pointer.  This is, in reality, `bipc::offset_ptr`.</span></div>
<div class="line"><a id="l00110" name="l00110"></a><span class="lineno">  110</span><span class="comment"> *   - Non-STL-compliant data structures with pointers, such as linked lists, can be written in terms</span></div>
<div class="line"><a id="l00111" name="l00111"></a><span class="lineno">  111</span><span class="comment"> *     of allocate() and deallocate(), but only if one uses #Pointer as opposed to raw `T*`</span></div>
<div class="line"><a id="l00112" name="l00112"></a><span class="lineno">  112</span><span class="comment"> *     pointers.  We recommend against this, but if it cannot be avoided due to legacy code or what-not....</span></div>
<div class="line"><a id="l00113" name="l00113"></a><span class="lineno">  113</span><span class="comment"> *</span></div>
<div class="line"><a id="l00114" name="l00114"></a><span class="lineno">  114</span><span class="comment"> * Handle borrowing support: Yes.  Pool_arena directly provides an API for this.  Internally it uses minimalistic</span></div>
<div class="line"><a id="l00115" name="l00115"></a><span class="lineno">  115</span><span class="comment"> * atomic ref-counting directly in SHM without any IPC messaging used.  Due to this internal simplicity this support</span></div>
<div class="line"><a id="l00116" name="l00116"></a><span class="lineno">  116</span><span class="comment"> * is symmetric and supports unlimited proxying out of the box.  That is, any process of N, each with a Pool_arena</span></div>
<div class="line"><a id="l00117" name="l00117"></a><span class="lineno">  117</span><span class="comment"> * open to the same pool named P, can construct a borrowable object, then lend it to any other process which can also</span></div>
<div class="line"><a id="l00118" name="l00118"></a><span class="lineno">  118</span><span class="comment"> * lend it to any other of the N processes.  Internally the last Pool_arena&#39;s borrowed (or originally lent)</span></div>
<div class="line"><a id="l00119" name="l00119"></a><span class="lineno">  119</span><span class="comment"> * handle to reach 0 intra-process ref-count shall invoke the object&#39;s dtor and deallocate the underlying buffer.</span></div>
<div class="line"><a id="l00120" name="l00120"></a><span class="lineno">  120</span><span class="comment"> * (Algorithms like this = why symmetric read/write capability is fairly central to Pool_arena as written.)</span></div>
<div class="line"><a id="l00121" name="l00121"></a><span class="lineno">  121</span><span class="comment"> *   - However, as of this writing, this support is deliberately basic.  In particular if a borrower process dies</span></div>
<div class="line"><a id="l00122" name="l00122"></a><span class="lineno">  122</span><span class="comment"> *     ungracefully (crash that does not execute all destructors, and so on), then the memory will leak until</span></div>
<div class="line"><a id="l00123" name="l00123"></a><span class="lineno">  123</span><span class="comment"> *     cleanup via remove_persistent().</span></div>
<div class="line"><a id="l00124" name="l00124"></a><span class="lineno">  124</span><span class="comment"> *</span></div>
<div class="line"><a id="l00125" name="l00125"></a><span class="lineno">  125</span><span class="comment"> * ### Allocation API and how to properly use it ###</span></div>
<div class="line"><a id="l00126" name="l00126"></a><span class="lineno">  126</span><span class="comment"> * The most basic and lowest-level API consists of allocate() and deallocate().  We recommend against</span></div>
<div class="line"><a id="l00127" name="l00127"></a><span class="lineno">  127</span><span class="comment"> * user code using these, as it is easy to leak and double-free (same as with `new` and `delete` in regular heap,</span></div>
<div class="line"><a id="l00128" name="l00128"></a><span class="lineno">  128</span><span class="comment"> * except as usual with SHM anything that was not allocated will persist in RAM until remove_persistent()).</span></div>
<div class="line"><a id="l00129" name="l00129"></a><span class="lineno">  129</span><span class="comment"> *   - shm::stl allocator(s) will use these APIs safely.</span></div>
<div class="line"><a id="l00130" name="l00130"></a><span class="lineno">  130</span><span class="comment"> *   - As noted earlier, if one writes a non-STL-compliant data structure (such as a manually written linked list),</span></div>
<div class="line"><a id="l00131" name="l00131"></a><span class="lineno">  131</span><span class="comment"> *     it is appropriate to use allocate(), deallocate(), and #Pointer.  It is best to avoid</span></div>
<div class="line"><a id="l00132" name="l00132"></a><span class="lineno">  132</span><span class="comment"> *     such data structures in favor of shm::stl-aided STL-compliant structures.</span></div>
<div class="line"><a id="l00133" name="l00133"></a><span class="lineno">  133</span><span class="comment"> *</span></div>
<div class="line"><a id="l00134" name="l00134"></a><span class="lineno">  134</span><span class="comment"> * The next level of API is construct().  `construct&lt;T&gt;()` returns a regular-looking `shared_ptr`.  If it is</span></div>
<div class="line"><a id="l00135" name="l00135"></a><span class="lineno">  135</span><span class="comment"> * never lent to another process, then the constructed `T` will be destroyed automatically as one would expect.</span></div>
<div class="line"><a id="l00136" name="l00136"></a><span class="lineno">  136</span><span class="comment"> * If one *does* properly lend such a `shared_ptr` (which we call a *handle*) to another process (and which it</span></div>
<div class="line"><a id="l00137" name="l00137"></a><span class="lineno">  137</span><span class="comment"> * can proxy-lend to another process still), then the `T` will be destroyed by the last process whose</span></div>
<div class="line"><a id="l00138" name="l00138"></a><span class="lineno">  138</span><span class="comment"> * handle reaches ref-count 0.  No explicit locking on the user&#39;s part is required to make this work.</span></div>
<div class="line"><a id="l00139" name="l00139"></a><span class="lineno">  139</span><span class="comment"> *   - If `T` is a POD (plain old data-type), then that&#39;s that.</span></div>
<div class="line"><a id="l00140" name="l00140"></a><span class="lineno">  140</span><span class="comment"> *   - If not, but `T` is a shm::stl-allocator-aided STL-compliant-structure, then you&#39;re good.</span></div>
<div class="line"><a id="l00141" name="l00141"></a><span class="lineno">  141</span><span class="comment"> *   - If not (e.g., the aforementioned manually implemented linked list) but the `T` destructor</span></div>
<div class="line"><a id="l00142" name="l00142"></a><span class="lineno">  142</span><span class="comment"> *     performs the necessary inner deallocation via deallocate(), then you&#39;re good.  Again, we recommend</span></div>
<div class="line"><a id="l00143" name="l00143"></a><span class="lineno">  143</span><span class="comment"> *     against this, but sometimes it cannot be helped.</span></div>
<div class="line"><a id="l00144" name="l00144"></a><span class="lineno">  144</span><span class="comment"> *   - If not, then one must manually do the inner deallocation first, then let the handle (`shared_ptr`) group</span></div>
<div class="line"><a id="l00145" name="l00145"></a><span class="lineno">  145</span><span class="comment"> *     reach ref-count 0.  The key is to do it in that order (which is why doing it via `T::~T()` is easiest).</span></div>
<div class="line"><a id="l00146" name="l00146"></a><span class="lineno">  146</span><span class="comment"> *</span></div>
<div class="line"><a id="l00147" name="l00147"></a><span class="lineno">  147</span><span class="comment"> * `T` cannot be a native array; and there is no facility for constructing such.  Use `std::array` or `boost::array`</span></div>
<div class="line"><a id="l00148" name="l00148"></a><span class="lineno">  148</span><span class="comment"> * as `T` if desired.</span></div>
<div class="line"><a id="l00149" name="l00149"></a><span class="lineno">  149</span><span class="comment"> */</span></div>
<div class="line"><a id="l00150" name="l00150"></a><span class="lineno"><a class="line" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html">  150</a></span><span class="keyword">class </span><a class="code hl_class" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html">Pool_arena</a> :</div>
<div class="line"><a id="l00151" name="l00151"></a><span class="lineno">  151</span>  <span class="keyword">public</span> flow::log::Log_context,</div>
<div class="line"><a id="l00152" name="l00152"></a><span class="lineno">  152</span>  <span class="keyword">private</span> boost::noncopyable</div>
<div class="line"><a id="l00153" name="l00153"></a><span class="lineno">  153</span>{</div>
<div class="line"><a id="l00154" name="l00154"></a><span class="lineno">  154</span><span class="keyword">public</span>:</div>
<div class="line"><a id="l00155" name="l00155"></a><span class="lineno">  155</span>  <span class="comment">// Types.</span></div>
<div class="line"><a id="l00156" name="l00156"></a><span class="lineno">  156</span><span class="comment"></span> </div>
<div class="line"><a id="l00157" name="l00157"></a><span class="lineno">  157</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00158" name="l00158"></a><span class="lineno">  158</span><span class="comment">   * SHM-storable fancy-pointer.  See class doc header for discussion.  Suitable for shm::stl allocator(s).</span></div>
<div class="line"><a id="l00159" name="l00159"></a><span class="lineno">  159</span><span class="comment">   *</span></div>
<div class="line"><a id="l00160" name="l00160"></a><span class="lineno">  160</span><span class="comment">   * @tparam T</span></div>
<div class="line"><a id="l00161" name="l00161"></a><span class="lineno">  161</span><span class="comment">   *         The pointed-to type.  `Pointer&lt;T&gt;` acts like `T*`.</span></div>
<div class="line"><a id="l00162" name="l00162"></a><span class="lineno">  162</span><span class="comment">   */</span></div>
<div class="line"><a id="l00163" name="l00163"></a><span class="lineno">  163</span>  <span class="keyword">template</span>&lt;<span class="keyword">typename</span> T&gt;</div>
<div class="line"><a id="l00164" name="l00164"></a><span class="lineno"><a class="line" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a07fec7ff0ba494dca0f0a010270cc35f">  164</a></span>  <span class="keyword">using </span><a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a07fec7ff0ba494dca0f0a010270cc35f">Pointer</a> = ::ipc::bipc::offset_ptr&lt;T&gt;;</div>
<div class="line"><a id="l00165" name="l00165"></a><span class="lineno">  165</span><span class="comment"></span> </div>
<div class="line"><a id="l00166" name="l00166"></a><span class="lineno">  166</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00167" name="l00167"></a><span class="lineno">  167</span><span class="comment">   * Outer handle to a SHM-stored object; really a regular-looking `shared_ptr` but with custom deleter</span></div>
<div class="line"><a id="l00168" name="l00168"></a><span class="lineno">  168</span><span class="comment">   * that ensures deallocation via Pool_arena as well as cross-process ref-count semantics.</span></div>
<div class="line"><a id="l00169" name="l00169"></a><span class="lineno">  169</span><span class="comment">   * See class doc header and construct().  A handle can also be lent/borrowed between processes;</span></div>
<div class="line"><a id="l00170" name="l00170"></a><span class="lineno">  170</span><span class="comment">   * see lend_object() and borrow_object().</span></div>
<div class="line"><a id="l00171" name="l00171"></a><span class="lineno">  171</span><span class="comment">   *</span></div>
<div class="line"><a id="l00172" name="l00172"></a><span class="lineno">  172</span><span class="comment">   * ### Rationale ###</span></div>
<div class="line"><a id="l00173" name="l00173"></a><span class="lineno">  173</span><span class="comment">   * Why have an alias, where it&#39;s a mere `shared_ptr`?  Two-fold reason:</span></div>
<div class="line"><a id="l00174" name="l00174"></a><span class="lineno">  174</span><span class="comment">   *   - (Mostly) While it *is* just `shared_ptr&lt;T&gt;`, and acts just as one would expect if borrow_object() and</span></div>
<div class="line"><a id="l00175" name="l00175"></a><span class="lineno">  175</span><span class="comment">   *     lend_object() are not involved, (1) it is an *outer* handle to a SHM-stored object, unlike the inner</span></div>
<div class="line"><a id="l00176" name="l00176"></a><span class="lineno">  176</span><span class="comment">   *     (subordinate) #Pointer values as maintained by STL-compliant logic or other data structure-internals code; and</span></div>
<div class="line"><a id="l00177" name="l00177"></a><span class="lineno">  177</span><span class="comment">   *     (2) it has special (if hopefully quite intuitive) capabilities of invoking ref-counting &quot;across&quot; processes</span></div>
<div class="line"><a id="l00178" name="l00178"></a><span class="lineno">  178</span><span class="comment">   *     via lend_object() and borrow_object().</span></div>
<div class="line"><a id="l00179" name="l00179"></a><span class="lineno">  179</span><span class="comment">   *   - (Minor) It&#39;s nice not to visibly impose a particular `shared_ptr` impl but kinda hide it behind an</span></div>
<div class="line"><a id="l00180" name="l00180"></a><span class="lineno">  180</span><span class="comment">   *     alias.  Ahem....</span></div>
<div class="line"><a id="l00181" name="l00181"></a><span class="lineno">  181</span><span class="comment">   *</span></div>
<div class="line"><a id="l00182" name="l00182"></a><span class="lineno">  182</span><span class="comment">   * @tparam T</span></div>
<div class="line"><a id="l00183" name="l00183"></a><span class="lineno">  183</span><span class="comment">   *         The pointed-to type.  Its dtor, informally, should ensure any inner deallocations subordinate</span></div>
<div class="line"><a id="l00184" name="l00184"></a><span class="lineno">  184</span><span class="comment">   *         to the managed `T` are performed before the `shared_ptr` reaches ref-count 0 in all processes</span></div>
<div class="line"><a id="l00185" name="l00185"></a><span class="lineno">  185</span><span class="comment">   *         to get the handle.  See class doc header.</span></div>
<div class="line"><a id="l00186" name="l00186"></a><span class="lineno">  186</span><span class="comment">   */</span></div>
<div class="line"><a id="l00187" name="l00187"></a><span class="lineno">  187</span>  <span class="keyword">template</span>&lt;<span class="keyword">typename</span> T&gt;</div>
<div class="line"><a id="l00188" name="l00188"></a><span class="lineno"><a class="line" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a662a55c9ba6eb5c389ddf9780ee801cb">  188</a></span>  <span class="keyword">using </span><a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a662a55c9ba6eb5c389ddf9780ee801cb">Handle</a> = boost::shared_ptr&lt;T&gt;;</div>
<div class="line"><a id="l00189" name="l00189"></a><span class="lineno">  189</span><span class="comment"></span> </div>
<div class="line"><a id="l00190" name="l00190"></a><span class="lineno">  190</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00191" name="l00191"></a><span class="lineno">  191</span><span class="comment">   * Alias for a light-weight blob.  They&#39;re little; TRACE-logging of deallocs and copies is of low value;</span></div>
<div class="line"><a id="l00192" name="l00192"></a><span class="lineno">  192</span><span class="comment">   * otherwise this can be switched to `flow::util::Blob`.</span></div>
<div class="line"><a id="l00193" name="l00193"></a><span class="lineno">  193</span><span class="comment">   */</span></div>
<div class="line"><a id="l00194" name="l00194"></a><span class="lineno"><a class="line" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a72867ce6e363dbc1ab1666768d8a7a09">  194</a></span>  <span class="keyword">using </span><a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a72867ce6e363dbc1ab1666768d8a7a09">Blob</a> = flow::util::Blob_sans_log_context;</div>
<div class="line"><a id="l00195" name="l00195"></a><span class="lineno">  195</span> </div>
<div class="line"><a id="l00196" name="l00196"></a><span class="lineno">  196</span>  <span class="comment">// Constructors/destructor.</span></div>
<div class="line"><a id="l00197" name="l00197"></a><span class="lineno">  197</span><span class="comment"></span> </div>
<div class="line"><a id="l00198" name="l00198"></a><span class="lineno">  198</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00199" name="l00199"></a><span class="lineno">  199</span><span class="comment">   * Construct Pool_arena accessor object to non-existing named SHM pool, creating it first.</span></div>
<div class="line"><a id="l00200" name="l00200"></a><span class="lineno">  200</span><span class="comment">   * If it already exists, it is an error.  If an error is emitted via `*err_code`, methods shall return</span></div>
<div class="line"><a id="l00201" name="l00201"></a><span class="lineno">  201</span><span class="comment">   * sentinel/`false` values.</span></div>
<div class="line"><a id="l00202" name="l00202"></a><span class="lineno">  202</span><span class="comment">   *</span></div>
<div class="line"><a id="l00203" name="l00203"></a><span class="lineno">  203</span><span class="comment">   * @param logger_ptr</span></div>
<div class="line"><a id="l00204" name="l00204"></a><span class="lineno">  204</span><span class="comment">   *        Logger to use for subsequently logging.</span></div>
<div class="line"><a id="l00205" name="l00205"></a><span class="lineno">  205</span><span class="comment">   * @param pool_name</span></div>
<div class="line"><a id="l00206" name="l00206"></a><span class="lineno">  206</span><span class="comment">   *        Absolute name at which the persistent SHM pool lives.</span></div>
<div class="line"><a id="l00207" name="l00207"></a><span class="lineno">  207</span><span class="comment">   * @param mode_tag</span></div>
<div class="line"><a id="l00208" name="l00208"></a><span class="lineno">  208</span><span class="comment">   *        API-choosing tag util::CREATE_ONLY.</span></div>
<div class="line"><a id="l00209" name="l00209"></a><span class="lineno">  209</span><span class="comment">   * @param perms</span></div>
<div class="line"><a id="l00210" name="l00210"></a><span class="lineno">  210</span><span class="comment">   *        Permissions to use for creation.  Suggest the use of util::shared_resource_permissions() to translate</span></div>
<div class="line"><a id="l00211" name="l00211"></a><span class="lineno">  211</span><span class="comment">   *        from one of a small handful of levels of access; these apply almost always in practice.</span></div>
<div class="line"><a id="l00212" name="l00212"></a><span class="lineno">  212</span><span class="comment">   *        The applied permissions shall *ignore* the process umask and shall thus exactly match `perms`,</span></div>
<div class="line"><a id="l00213" name="l00213"></a><span class="lineno">  213</span><span class="comment">   *        unless an error occurs.</span></div>
<div class="line"><a id="l00214" name="l00214"></a><span class="lineno">  214</span><span class="comment">   * @param pool_sz</span></div>
<div class="line"><a id="l00215" name="l00215"></a><span class="lineno">  215</span><span class="comment">   *        Pool size.  Note: OS, namely Linux, shall not in fact take (necessarily) this full amount from general</span></div>
<div class="line"><a id="l00216" name="l00216"></a><span class="lineno">  216</span><span class="comment">   *        availability but rather a small amount.  Chunks of RAM (pages) shall be later reserved as they begin to</span></div>
<div class="line"><a id="l00217" name="l00217"></a><span class="lineno">  217</span><span class="comment">   *        be used, namely via the allocation API.  It may be viable to set this to a quite large value to</span></div>
<div class="line"><a id="l00218" name="l00218"></a><span class="lineno">  218</span><span class="comment">   *        avoid running out of pool space.  However watch out for (typically configurable) kernel parameters</span></div>
<div class="line"><a id="l00219" name="l00219"></a><span class="lineno">  219</span><span class="comment">   *        as to the sum of sizes of active pools.</span></div>
<div class="line"><a id="l00220" name="l00220"></a><span class="lineno">  220</span><span class="comment">   * @param err_code</span></div>
<div class="line"><a id="l00221" name="l00221"></a><span class="lineno">  221</span><span class="comment">   *        See `flow::Error_code` docs for error reporting semantics.  #Error_code generated:</span></div>
<div class="line"><a id="l00222" name="l00222"></a><span class="lineno">  222</span><span class="comment">   *        various.  Most likely creation failed due to permissions, or it already existed.</span></div>
<div class="line"><a id="l00223" name="l00223"></a><span class="lineno">  223</span><span class="comment">   *        An `ENOSPC` (No space left on device) error means the aforementioned kernel parameter has been</span></div>
<div class="line"><a id="l00224" name="l00224"></a><span class="lineno">  224</span><span class="comment">   *        hit (Linux at least); pool size rebalancing in your overall system may be required (or else one</span></div>
<div class="line"><a id="l00225" name="l00225"></a><span class="lineno">  225</span><span class="comment">   *        might tweak the relevant kernel parameter(s)).</span></div>
<div class="line"><a id="l00226" name="l00226"></a><span class="lineno">  226</span><span class="comment">   */</span></div>
<div class="line"><a id="l00227" name="l00227"></a><span class="lineno">  227</span>  <span class="keyword">explicit</span> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a77acacecacdd45514ebf9db99b4ab4c3">Pool_arena</a>(flow::log::Logger* logger_ptr, <span class="keyword">const</span> <a class="code hl_class" href="classipc_1_1util_1_1Shared__name.html">Shared_name</a>&amp; pool_name,</div>
<div class="line"><a id="l00228" name="l00228"></a><span class="lineno">  228</span>                      <a class="code hl_typedef" href="namespaceipc_1_1util.html#a9d84c2bab504e6de32b20c77ca9723a2">util::Create_only</a> mode_tag, <span class="keywordtype">size_t</span> pool_sz,</div>
<div class="line"><a id="l00229" name="l00229"></a><span class="lineno">  229</span>                      <span class="keyword">const</span> <a class="code hl_typedef" href="namespaceipc_1_1util.html#a1b398ae730d1e6040687cb2397115152">util::Permissions</a>&amp; perms = <a class="code hl_typedef" href="namespaceipc_1_1util.html#a1b398ae730d1e6040687cb2397115152">util::Permissions</a>{}, <a class="code hl_typedef" href="namespaceipc.html#aa3192e586cc45d3e7c22463bf2760f89">Error_code</a>* err_code = <span class="keyword">nullptr</span>);</div>
<div class="line"><a id="l00230" name="l00230"></a><span class="lineno">  230</span><span class="comment"></span> </div>
<div class="line"><a id="l00231" name="l00231"></a><span class="lineno">  231</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00232" name="l00232"></a><span class="lineno">  232</span><span class="comment">   * Construct Pool_arena accessor object to non-existing named SHM pool, or else if it does not exist creates it</span></div>
<div class="line"><a id="l00233" name="l00233"></a><span class="lineno">  233</span><span class="comment">   * first and opens it (atomically).  If an error is emitted via `*err_code`, methods shall return</span></div>
<div class="line"><a id="l00234" name="l00234"></a><span class="lineno">  234</span><span class="comment">   * sentinel/`false` values.</span></div>
<div class="line"><a id="l00235" name="l00235"></a><span class="lineno">  235</span><span class="comment">   *</span></div>
<div class="line"><a id="l00236" name="l00236"></a><span class="lineno">  236</span><span class="comment">   * @param logger_ptr</span></div>
<div class="line"><a id="l00237" name="l00237"></a><span class="lineno">  237</span><span class="comment">   *        Logger to use for subsequently logging.</span></div>
<div class="line"><a id="l00238" name="l00238"></a><span class="lineno">  238</span><span class="comment">   * @param pool_name</span></div>
<div class="line"><a id="l00239" name="l00239"></a><span class="lineno">  239</span><span class="comment">   *        Absolute name at which the persistent SHM pool lives.</span></div>
<div class="line"><a id="l00240" name="l00240"></a><span class="lineno">  240</span><span class="comment">   * @param mode_tag</span></div>
<div class="line"><a id="l00241" name="l00241"></a><span class="lineno">  241</span><span class="comment">   *        API-choosing tag util::OPEN_OR_CREATE.</span></div>
<div class="line"><a id="l00242" name="l00242"></a><span class="lineno">  242</span><span class="comment">   * @param perms_on_create</span></div>
<div class="line"><a id="l00243" name="l00243"></a><span class="lineno">  243</span><span class="comment">   *        Permissions to use for creation.  Suggest the use of util::shared_resource_permissions() to translate</span></div>
<div class="line"><a id="l00244" name="l00244"></a><span class="lineno">  244</span><span class="comment">   *        from one of a small handful of levels of access; these apply almost always in practice.</span></div>
<div class="line"><a id="l00245" name="l00245"></a><span class="lineno">  245</span><span class="comment">   *        The applied permissions shall *ignore* the process umask and shall thus exactly match `perms_on_create`,</span></div>
<div class="line"><a id="l00246" name="l00246"></a><span class="lineno">  246</span><span class="comment">   *        unless an error occurs.</span></div>
<div class="line"><a id="l00247" name="l00247"></a><span class="lineno">  247</span><span class="comment">   * @param pool_sz</span></div>
<div class="line"><a id="l00248" name="l00248"></a><span class="lineno">  248</span><span class="comment">   *        Pool size.  See note in first ctor.</span></div>
<div class="line"><a id="l00249" name="l00249"></a><span class="lineno">  249</span><span class="comment">   * @param err_code</span></div>
<div class="line"><a id="l00250" name="l00250"></a><span class="lineno">  250</span><span class="comment">   *        See `flow::Error_code` docs for error reporting semantics.  #Error_code generated:</span></div>
<div class="line"><a id="l00251" name="l00251"></a><span class="lineno">  251</span><span class="comment">   *        various.  Most likely creation failed due to permissions, or it already existed.</span></div>
<div class="line"><a id="l00252" name="l00252"></a><span class="lineno">  252</span><span class="comment">   */</span></div>
<div class="line"><a id="l00253" name="l00253"></a><span class="lineno">  253</span>  <span class="keyword">explicit</span> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a77acacecacdd45514ebf9db99b4ab4c3">Pool_arena</a>(flow::log::Logger* logger_ptr, <span class="keyword">const</span> <a class="code hl_class" href="classipc_1_1util_1_1Shared__name.html">Shared_name</a>&amp; pool_name,</div>
<div class="line"><a id="l00254" name="l00254"></a><span class="lineno">  254</span>                      <a class="code hl_typedef" href="namespaceipc_1_1util.html#a9571de958538d7a4a8649bbfecfac0b9">util::Open_or_create</a> mode_tag, <span class="keywordtype">size_t</span> pool_sz,</div>
<div class="line"><a id="l00255" name="l00255"></a><span class="lineno">  255</span>                      <span class="keyword">const</span> <a class="code hl_typedef" href="namespaceipc_1_1util.html#a1b398ae730d1e6040687cb2397115152">util::Permissions</a>&amp; perms_on_create = <a class="code hl_typedef" href="namespaceipc_1_1util.html#a1b398ae730d1e6040687cb2397115152">util::Permissions</a>{}, <a class="code hl_typedef" href="namespaceipc.html#aa3192e586cc45d3e7c22463bf2760f89">Error_code</a>* err_code = <span class="keyword">nullptr</span>);</div>
<div class="line"><a id="l00256" name="l00256"></a><span class="lineno">  256</span><span class="comment"></span> </div>
<div class="line"><a id="l00257" name="l00257"></a><span class="lineno">  257</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00258" name="l00258"></a><span class="lineno">  258</span><span class="comment">   * Construct Pool_arena accessor object to existing named SHM pool.  If it does not exist, it is an error.</span></div>
<div class="line"><a id="l00259" name="l00259"></a><span class="lineno">  259</span><span class="comment">   * If an error is emitted via `*err_code`, methods shall return sentinel/`false` values.</span></div>
<div class="line"><a id="l00260" name="l00260"></a><span class="lineno">  260</span><span class="comment">   *</span></div>
<div class="line"><a id="l00261" name="l00261"></a><span class="lineno">  261</span><span class="comment">   * @param logger_ptr</span></div>
<div class="line"><a id="l00262" name="l00262"></a><span class="lineno">  262</span><span class="comment">   *        Logger to use for subsequently logging.</span></div>
<div class="line"><a id="l00263" name="l00263"></a><span class="lineno">  263</span><span class="comment">   * @param pool_name</span></div>
<div class="line"><a id="l00264" name="l00264"></a><span class="lineno">  264</span><span class="comment">   *        Absolute name at which the persistent SHM pool lives.</span></div>
<div class="line"><a id="l00265" name="l00265"></a><span class="lineno">  265</span><span class="comment">   * @param mode_tag</span></div>
<div class="line"><a id="l00266" name="l00266"></a><span class="lineno">  266</span><span class="comment">   *        API-choosing tag util::OPEN_ONLY.</span></div>
<div class="line"><a id="l00267" name="l00267"></a><span class="lineno">  267</span><span class="comment">   * @param read_only</span></div>
<div class="line"><a id="l00268" name="l00268"></a><span class="lineno">  268</span><span class="comment">   *        If and only if `true` the calling process will be prevented by the OS from writing into the pages</span></div>
<div class="line"><a id="l00269" name="l00269"></a><span class="lineno">  269</span><span class="comment">   *        mapped by `*this` subsequently.  Such attempts will lead to undefined behavior.</span></div>
<div class="line"><a id="l00270" name="l00270"></a><span class="lineno">  270</span><span class="comment">   *        Note that this includes any attempt at allocating as well as writing into allocated (or otherwise)</span></div>
<div class="line"><a id="l00271" name="l00271"></a><span class="lineno">  271</span><span class="comment">   *        address space.  Further note that, internally, deallocation -- directly or otherwise -- involves</span></div>
<div class="line"><a id="l00272" name="l00272"></a><span class="lineno">  272</span><span class="comment">   *        (in this implementation) writing and is thus also disallowed.    Lastly, and quite significantly,</span></div>
<div class="line"><a id="l00273" name="l00273"></a><span class="lineno">  273</span><span class="comment">   *        borrow_object() can be called, but undefined behavior shall result when the resulting `shared_ptr`</span></div>
<div class="line"><a id="l00274" name="l00274"></a><span class="lineno">  274</span><span class="comment">   *        (#Handle) group reaches ref-count 0, as internally that requires a decrement of a counter (which is</span></div>
<div class="line"><a id="l00275" name="l00275"></a><span class="lineno">  275</span><span class="comment">   *        a write).  Therefore borrow_object() cannot be used either.  Therefore it is up to you, in that</span></div>
<div class="line"><a id="l00276" name="l00276"></a><span class="lineno">  276</span><span class="comment">   *        case, to (1) never call deallocate() directly or otherwise (i.e., through an allocator);</span></div>
<div class="line"><a id="l00277" name="l00277"></a><span class="lineno">  277</span><span class="comment">   *        and (2) to design your algorithms in such a way as to never require lending to this Pool_arena.</span></div>
<div class="line"><a id="l00278" name="l00278"></a><span class="lineno">  278</span><span class="comment">   *        In practice this would be quite a low-level, stunted use of `Pool_arena` across 2+ processes;</span></div>
<div class="line"><a id="l00279" name="l00279"></a><span class="lineno">  279</span><span class="comment">   *        but it is not necessarily useless.  (There might be, say, test/debug/reporting use cases.)</span></div>
<div class="line"><a id="l00280" name="l00280"></a><span class="lineno">  280</span><span class="comment">   * @param err_code</span></div>
<div class="line"><a id="l00281" name="l00281"></a><span class="lineno">  281</span><span class="comment">   *        See `flow::Error_code` docs for error reporting semantics.  #Error_code generated:</span></div>
<div class="line"><a id="l00282" name="l00282"></a><span class="lineno">  282</span><span class="comment">   *        various.  Most likely creation failed due to permissions, or it already existed.</span></div>
<div class="line"><a id="l00283" name="l00283"></a><span class="lineno">  283</span><span class="comment">   */</span></div>
<div class="line"><a id="l00284" name="l00284"></a><span class="lineno">  284</span>  <span class="keyword">explicit</span> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a77acacecacdd45514ebf9db99b4ab4c3">Pool_arena</a>(flow::log::Logger* logger_ptr, <span class="keyword">const</span> <a class="code hl_typedef" href="namespaceipc_1_1shm_1_1classic.html#ac0a52218467710995cc6c74538be6012">Shared_name</a>&amp; pool_name,</div>
<div class="line"><a id="l00285" name="l00285"></a><span class="lineno">  285</span>                      <a class="code hl_typedef" href="namespaceipc_1_1util.html#a3e03491b5b2b5fac26551a220946d6e5">util::Open_only</a> mode_tag, <span class="keywordtype">bool</span> read_only = <span class="keyword">false</span>, <a class="code hl_typedef" href="namespaceipc.html#aa3192e586cc45d3e7c22463bf2760f89">Error_code</a>* err_code = <span class="keyword">nullptr</span>);</div>
<div class="line"><a id="l00286" name="l00286"></a><span class="lineno">  286</span><span class="comment"></span> </div>
<div class="line"><a id="l00287" name="l00287"></a><span class="lineno">  287</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00288" name="l00288"></a><span class="lineno">  288</span><span class="comment">   * Destroys Pool_arena accessor object.  In and of itself this does not destroy the underlying pool named</span></div>
<div class="line"><a id="l00289" name="l00289"></a><span class="lineno">  289</span><span class="comment">   * #m_pool_name; it continues to exist as long as (1) any other similar accessor objects (or other OS-created</span></div>
<div class="line"><a id="l00290" name="l00290"></a><span class="lineno">  290</span><span class="comment">   * handles) do; and/or (2) its entry in the file system lives (hence until remove_persistent() is called</span></div>
<div class="line"><a id="l00291" name="l00291"></a><span class="lineno">  291</span><span class="comment">   * for #m_pool_name).  This is analogous to closing a descriptor to a file.</span></div>
<div class="line"><a id="l00292" name="l00292"></a><span class="lineno">  292</span><span class="comment">   */</span></div>
<div class="line"><a id="l00293" name="l00293"></a><span class="lineno">  293</span>  <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#aca8bf9fe738df70fd502111330089c90">~Pool_arena</a>();</div>
<div class="line"><a id="l00294" name="l00294"></a><span class="lineno">  294</span> </div>
<div class="line"><a id="l00295" name="l00295"></a><span class="lineno">  295</span>  <span class="comment">// Methods.</span></div>
<div class="line"><a id="l00296" name="l00296"></a><span class="lineno">  296</span><span class="comment"></span> </div>
<div class="line"><a id="l00297" name="l00297"></a><span class="lineno">  297</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00298" name="l00298"></a><span class="lineno">  298</span><span class="comment">   * Removes the named SHM pool object.  The name `name` is removed from the system immediately; and</span></div>
<div class="line"><a id="l00299" name="l00299"></a><span class="lineno">  299</span><span class="comment">   * the function is non-blocking.  However the underlying pool if any continues to exist until all handles</span></div>
<div class="line"><a id="l00300" name="l00300"></a><span class="lineno">  300</span><span class="comment">   * (accessor objects Pool_arena or other OS-created handles) to it are closed; their presence in this or other</span></div>
<div class="line"><a id="l00301" name="l00301"></a><span class="lineno">  301</span><span class="comment">   * process is *not* an error.  See also dtor doc header for related notes.</span></div>
<div class="line"><a id="l00302" name="l00302"></a><span class="lineno">  302</span><span class="comment">   *</span></div>
<div class="line"><a id="l00303" name="l00303"></a><span class="lineno">  303</span><span class="comment">   * @note The specified pool need not have been created via a Pool_arena object; it can be any pool</span></div>
<div class="line"><a id="l00304" name="l00304"></a><span class="lineno">  304</span><span class="comment">   *       created by name ultimately via OS `shm_open()` or equivalent call.  Therefore this is a utility</span></div>
<div class="line"><a id="l00305" name="l00305"></a><span class="lineno">  305</span><span class="comment">   *       that is not limited for use in the ipc::shm::classic context.</span></div>
<div class="line"><a id="l00306" name="l00306"></a><span class="lineno">  306</span><span class="comment">   * @see `util::remove_each_persistent_*`() for a convenient way to remove more than one item.  E.g.,</span></div>
<div class="line"><a id="l00307" name="l00307"></a><span class="lineno">  307</span><span class="comment">   *      `util::remove_each_persistent_with_name_prefix&lt;Pool_arena&gt;()` combines remove_persistent() and</span></div>
<div class="line"><a id="l00308" name="l00308"></a><span class="lineno">  308</span><span class="comment">   *      for_each_persistent() in a common-sense way to remove only those `name`s starting with a given prefix;</span></div>
<div class="line"><a id="l00309" name="l00309"></a><span class="lineno">  309</span><span class="comment">   *      or simply all of them.</span></div>
<div class="line"><a id="l00310" name="l00310"></a><span class="lineno">  310</span><span class="comment">   *</span></div>
<div class="line"><a id="l00311" name="l00311"></a><span class="lineno">  311</span><span class="comment">   * Trying to remove a non-existent name *is* an error.</span></div>
<div class="line"><a id="l00312" name="l00312"></a><span class="lineno">  312</span><span class="comment">   *</span></div>
<div class="line"><a id="l00313" name="l00313"></a><span class="lineno">  313</span><span class="comment">   * Logs INFO message.</span></div>
<div class="line"><a id="l00314" name="l00314"></a><span class="lineno">  314</span><span class="comment">   *</span></div>
<div class="line"><a id="l00315" name="l00315"></a><span class="lineno">  315</span><span class="comment">   * @param logger_ptr</span></div>
<div class="line"><a id="l00316" name="l00316"></a><span class="lineno">  316</span><span class="comment">   *        Logger to use for subsequently logging.</span></div>
<div class="line"><a id="l00317" name="l00317"></a><span class="lineno">  317</span><span class="comment">   * @param name</span></div>
<div class="line"><a id="l00318" name="l00318"></a><span class="lineno">  318</span><span class="comment">   *        Absolute name at which the persistent SHM pool lives.</span></div>
<div class="line"><a id="l00319" name="l00319"></a><span class="lineno">  319</span><span class="comment">   * @param err_code</span></div>
<div class="line"><a id="l00320" name="l00320"></a><span class="lineno">  320</span><span class="comment">   *        See `flow::Error_code` docs for error reporting semantics.  #Error_code generated:</span></div>
<div class="line"><a id="l00321" name="l00321"></a><span class="lineno">  321</span><span class="comment">   *        various.  Most likely it&#39;ll be a not-found error or permissions error.</span></div>
<div class="line"><a id="l00322" name="l00322"></a><span class="lineno">  322</span><span class="comment">   */</span></div>
<div class="line"><a id="l00323" name="l00323"></a><span class="lineno">  323</span>  <span class="keyword">static</span> <span class="keywordtype">void</span> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a9487dcff44fde9a2c12d64b51c16c85e">remove_persistent</a>(flow::log::Logger* logger_ptr, <span class="keyword">const</span> <a class="code hl_typedef" href="namespaceipc_1_1shm_1_1classic.html#ac0a52218467710995cc6c74538be6012">Shared_name</a>&amp; name,</div>
<div class="line"><a id="l00324" name="l00324"></a><span class="lineno">  324</span>                                <a class="code hl_typedef" href="namespaceipc.html#aa3192e586cc45d3e7c22463bf2760f89">Error_code</a>* err_code = <span class="keyword">nullptr</span>);</div>
<div class="line"><a id="l00325" name="l00325"></a><span class="lineno">  325</span><span class="comment"></span> </div>
<div class="line"><a id="l00326" name="l00326"></a><span class="lineno">  326</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00327" name="l00327"></a><span class="lineno">  327</span><span class="comment">   * Lists all named SHM pool objects currently persisting, invoking the given handler synchronously on each one.</span></div>
<div class="line"><a id="l00328" name="l00328"></a><span class="lineno">  328</span><span class="comment">   *</span></div>
<div class="line"><a id="l00329" name="l00329"></a><span class="lineno">  329</span><span class="comment">   * Note that, in a sanely set-up OS install, all existing pools will be listed by this function;</span></div>
<div class="line"><a id="l00330" name="l00330"></a><span class="lineno">  330</span><span class="comment">   * but permissions/ownership may forbid certain operations the user may typically want to invoke on</span></div>
<div class="line"><a id="l00331" name="l00331"></a><span class="lineno">  331</span><span class="comment">   * a given listed name -- for example remove_persistent().  This function does *not* filter-out any</span></div>
<div class="line"><a id="l00332" name="l00332"></a><span class="lineno">  332</span><span class="comment">   * potentially inaccessible items.</span></div>
<div class="line"><a id="l00333" name="l00333"></a><span class="lineno">  333</span><span class="comment">   *</span></div>
<div class="line"><a id="l00334" name="l00334"></a><span class="lineno">  334</span><span class="comment">   * @note The listed pools need not have been created via Pool_arena objects; they will be all pools</span></div>
<div class="line"><a id="l00335" name="l00335"></a><span class="lineno">  335</span><span class="comment">   *       created by name ultimately via OS `shm_open()` or equivalent call.  Therefore this is a utility</span></div>
<div class="line"><a id="l00336" name="l00336"></a><span class="lineno">  336</span><span class="comment">   *       that is not limited for use in the ipc::shm::classic context.</span></div>
<div class="line"><a id="l00337" name="l00337"></a><span class="lineno">  337</span><span class="comment">   *</span></div>
<div class="line"><a id="l00338" name="l00338"></a><span class="lineno">  338</span><span class="comment">   * @tparam Handle_name_func</span></div>
<div class="line"><a id="l00339" name="l00339"></a><span class="lineno">  339</span><span class="comment">   *         Function object matching signature `void F(const Shared_name&amp;)`.</span></div>
<div class="line"><a id="l00340" name="l00340"></a><span class="lineno">  340</span><span class="comment">   * @param handle_name_func</span></div>
<div class="line"><a id="l00341" name="l00341"></a><span class="lineno">  341</span><span class="comment">   *        `handle_name_func()` shall be invoked for each item.  See `Handle_name_func`.</span></div>
<div class="line"><a id="l00342" name="l00342"></a><span class="lineno">  342</span><span class="comment">   */</span></div>
<div class="line"><a id="l00343" name="l00343"></a><span class="lineno">  343</span>  <span class="keyword">template</span>&lt;<span class="keyword">typename</span> Handle_name_func&gt;</div>
<div class="line"><a id="l00344" name="l00344"></a><span class="lineno">  344</span>  <span class="keyword">static</span> <span class="keywordtype">void</span> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a9e720283945eefe3d941b185e95d2ce1">for_each_persistent</a>(<span class="keyword">const</span> Handle_name_func&amp; handle_name_func);</div>
<div class="line"><a id="l00345" name="l00345"></a><span class="lineno">  345</span><span class="comment"></span> </div>
<div class="line"><a id="l00346" name="l00346"></a><span class="lineno">  346</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00347" name="l00347"></a><span class="lineno">  347</span><span class="comment">   * Allocates buffer of specified size, in bytes, in the accessed pool; returns locally-derefernceable address</span></div>
<div class="line"><a id="l00348" name="l00348"></a><span class="lineno">  348</span><span class="comment">   * to the first byte.  Returns null if no pool attached to `*this`.  Throws exception if ran out of space.</span></div>
<div class="line"><a id="l00349" name="l00349"></a><span class="lineno">  349</span><span class="comment">   *</span></div>
<div class="line"><a id="l00350" name="l00350"></a><span class="lineno">  350</span><span class="comment">   * Take care to only use this when and as appropriate; see class doc header notes on this.</span></div>
<div class="line"><a id="l00351" name="l00351"></a><span class="lineno">  351</span><span class="comment">   *</span></div>
<div class="line"><a id="l00352" name="l00352"></a><span class="lineno">  352</span><span class="comment">   * ### Rationale for throwing exception instead of returning null ###</span></div>
<div class="line"><a id="l00353" name="l00353"></a><span class="lineno">  353</span><span class="comment">   * This does go against the precedent in most of ::ipc, which either returns sentinel values or uses</span></div>
<div class="line"><a id="l00354" name="l00354"></a><span class="lineno">  354</span><span class="comment">   * Flow-style #Error_code based emission (out-arg or exception).  The original reason may appear somewhat arbitrary</span></div>
<div class="line"><a id="l00355" name="l00355"></a><span class="lineno">  355</span><span class="comment">   * and is 2-fold:</span></div>
<div class="line"><a id="l00356" name="l00356"></a><span class="lineno">  356</span><span class="comment">   *   - It&#39;s what bipc does (throws `bipc::bad_alloc_exception`), and indeed we propagate what it throws.</span></div>
<div class="line"><a id="l00357" name="l00357"></a><span class="lineno">  357</span><span class="comment">   *   - It&#39;s what STL-compliant allocators (such as our own in shm::stl) must do; and they will invoke this</span></div>
<div class="line"><a id="l00358" name="l00358"></a><span class="lineno">  358</span><span class="comment">   *     (certainly not exclusively).</span></div>
<div class="line"><a id="l00359" name="l00359"></a><span class="lineno">  359</span><span class="comment">   *</span></div>
<div class="line"><a id="l00360" name="l00360"></a><span class="lineno">  360</span><span class="comment">   * I (ygoldfel) claim it&#39;s a matter of... synergy, maybe, or tradition.  It really is an exceptional situation to</span></div>
<div class="line"><a id="l00361" name="l00361"></a><span class="lineno">  361</span><span class="comment">   * run out of pool space.  Supposing some system is built on-top of N pools, of which `*this` is one, it can certainly</span></div>
<div class="line"><a id="l00362" name="l00362"></a><span class="lineno">  362</span><span class="comment">   * catch it (and in that case it shouldn&#39;t be frequent enough to seriously affect perf by virtue of slowness</span></div>
<div class="line"><a id="l00363" name="l00363"></a><span class="lineno">  363</span><span class="comment">   * of exception-throwing/catching) and use another pool.  Granted, it could use Flow semantics, which would throw</span></div>
<div class="line"><a id="l00364" name="l00364"></a><span class="lineno">  364</span><span class="comment">   * only if an `Error_code*` supplied were null, but that misses the point that allocate() failing to</span></div>
<div class="line"><a id="l00365" name="l00365"></a><span class="lineno">  365</span><span class="comment">   * allocate due to lack of space is the only thing that can really go wrong and is exceptional.  Adding</span></div>
<div class="line"><a id="l00366" name="l00366"></a><span class="lineno">  366</span><span class="comment">   * an `Error_code* err_code` out-arg would hardly add much value.</span></div>
<div class="line"><a id="l00367" name="l00367"></a><span class="lineno">  367</span><span class="comment">   *</span></div>
<div class="line"><a id="l00368" name="l00368"></a><span class="lineno">  368</span><span class="comment">   * @param n</span></div>
<div class="line"><a id="l00369" name="l00369"></a><span class="lineno">  369</span><span class="comment">   *        Desired buffer size in bytes.  Must not be 0 (behavior undefined/assertion may trip).</span></div>
<div class="line"><a id="l00370" name="l00370"></a><span class="lineno">  370</span><span class="comment">   * @return Non-null on success (see above); null if ctor failed to attach pool.</span></div>
<div class="line"><a id="l00371" name="l00371"></a><span class="lineno">  371</span><span class="comment">   */</span></div>
<div class="line"><a id="l00372" name="l00372"></a><span class="lineno">  372</span>  <span class="keywordtype">void</span>* <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a9da3a100a0b7199644edbadacc9083c9">allocate</a>(<span class="keywordtype">size_t</span> n);</div>
<div class="line"><a id="l00373" name="l00373"></a><span class="lineno">  373</span><span class="comment"></span> </div>
<div class="line"><a id="l00374" name="l00374"></a><span class="lineno">  374</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00375" name="l00375"></a><span class="lineno">  375</span><span class="comment">   * Undoes effects of local allocate() that returned `buf_not_null`; or another-process&#39;s</span></div>
<div class="line"><a id="l00376" name="l00376"></a><span class="lineno">  376</span><span class="comment">   * allocate() that returned pointer whose locally-dereferenceable equivalent is `but_not_null`.</span></div>
<div class="line"><a id="l00377" name="l00377"></a><span class="lineno">  377</span><span class="comment">   * Returns `false` if and only if no pool attached to `*this`.  Does not throw exception.  Behavior is</span></div>
<div class="line"><a id="l00378" name="l00378"></a><span class="lineno">  378</span><span class="comment">   * undefined if `buf_not_null` is not as described above; in particular if it is null.</span></div>
<div class="line"><a id="l00379" name="l00379"></a><span class="lineno">  379</span><span class="comment">   *</span></div>
<div class="line"><a id="l00380" name="l00380"></a><span class="lineno">  380</span><span class="comment">   * @param buf_not_null</span></div>
<div class="line"><a id="l00381" name="l00381"></a><span class="lineno">  381</span><span class="comment">   *        See above.</span></div>
<div class="line"><a id="l00382" name="l00382"></a><span class="lineno">  382</span><span class="comment">   * @return `true` on success; `false` if ctor failed to attach a pool.</span></div>
<div class="line"><a id="l00383" name="l00383"></a><span class="lineno">  383</span><span class="comment">   */</span></div>
<div class="line"><a id="l00384" name="l00384"></a><span class="lineno">  384</span>  <span class="keywordtype">bool</span> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a394973b7cfb67b67113043810804337d">deallocate</a>(<span class="keywordtype">void</span>* buf_not_null) <span class="keyword">noexcept</span>;</div>
<div class="line"><a id="l00385" name="l00385"></a><span class="lineno">  385</span><span class="comment"></span> </div>
<div class="line"><a id="l00386" name="l00386"></a><span class="lineno">  386</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00387" name="l00387"></a><span class="lineno">  387</span><span class="comment">   * Constructs an object of given type with given ctor args, having allocated space directly in attached</span></div>
<div class="line"><a id="l00388" name="l00388"></a><span class="lineno">  388</span><span class="comment">   * SHM pool, and returns a ref-counted handle that (1) guarantees destruction and deallocation shall occur</span></div>
<div class="line"><a id="l00389" name="l00389"></a><span class="lineno">  389</span><span class="comment">   * once no owners hold a reference; and (2) can be lent to other processes (and other processes still</span></div>
<div class="line"><a id="l00390" name="l00390"></a><span class="lineno">  390</span><span class="comment">   * indefinitely), thus adding owners beyond this process, via lend_object()/borrow_object().</span></div>
<div class="line"><a id="l00391" name="l00391"></a><span class="lineno">  391</span><span class="comment">   * Returns null if no pool attached to `*this`.  Throws exception if ran out of space.</span></div>
<div class="line"><a id="l00392" name="l00392"></a><span class="lineno">  392</span><span class="comment">   *</span></div>
<div class="line"><a id="l00393" name="l00393"></a><span class="lineno">  393</span><span class="comment">   * Is better to use this than allocate() whenever possible; see class doc header notes on this.</span></div>
<div class="line"><a id="l00394" name="l00394"></a><span class="lineno">  394</span><span class="comment">   *</span></div>
<div class="line"><a id="l00395" name="l00395"></a><span class="lineno">  395</span><span class="comment">   * Note that that there is no way to `construct()` a native array.  If that is your aim please use</span></div>
<div class="line"><a id="l00396" name="l00396"></a><span class="lineno">  396</span><span class="comment">   * `T = std::array&lt;&gt;` or similar.</span></div>
<div class="line"><a id="l00397" name="l00397"></a><span class="lineno">  397</span><span class="comment">   *</span></div>
<div class="line"><a id="l00398" name="l00398"></a><span class="lineno">  398</span><span class="comment">   * ### Integration with shm::stl::Stateless_allocator ###</span></div>
<div class="line"><a id="l00399" name="l00399"></a><span class="lineno">  399</span><span class="comment">   * This method, bracketing the invocation of the `T` ctor, sets the thread-local</span></div>
<div class="line"><a id="l00400" name="l00400"></a><span class="lineno">  400</span><span class="comment">   * `shm::stl::Arena_activator&lt;Pool_arena&gt;` context to `this`.  Therefore the caller need not do so.</span></div>
<div class="line"><a id="l00401" name="l00401"></a><span class="lineno">  401</span><span class="comment">   * If `T` does not store an STL-compliant structure that uses `Stateless_allocator`, then this is harmless</span></div>
<div class="line"><a id="l00402" name="l00402"></a><span class="lineno">  402</span><span class="comment">   * albeit a small perf hit.  If `T` does do so, then it is a convenience.</span></div>
<div class="line"><a id="l00403" name="l00403"></a><span class="lineno">  403</span><span class="comment">   *</span></div>
<div class="line"><a id="l00404" name="l00404"></a><span class="lineno">  404</span><span class="comment">   * Arguably more importantly: The returned `shared_ptr` is such that when garbage-collection of the created</span></div>
<div class="line"><a id="l00405" name="l00405"></a><span class="lineno">  405</span><span class="comment">   * data structure does occur -- which may occur in this process, but via lend_object() and borrow_object()</span></div>
<div class="line"><a id="l00406" name="l00406"></a><span class="lineno">  406</span><span class="comment">   * may well occur in another process -- the `T::~T()` *dtor* call shall also be bracketed by the aforementioned</span></div>
<div class="line"><a id="l00407" name="l00407"></a><span class="lineno">  407</span><span class="comment">   * context.  Again: If `T` does not rely on `Stateless_allocator`, then it&#39;s harmless; but if it *does* then</span></div>
<div class="line"><a id="l00408" name="l00408"></a><span class="lineno">  408</span><span class="comment">   * doing this is quite essential.  That is because the user cannot, typically (or at least sufficiently easily),</span></div>
<div class="line"><a id="l00409" name="l00409"></a><span class="lineno">  409</span><span class="comment">   * control the per-thread allocator context at the time of dtor call -- simply because who knows who or what</span></div>
<div class="line"><a id="l00410" name="l00410"></a><span class="lineno">  410</span><span class="comment">   * will be running when the cross-process ref-count reaches 0.</span></div>
<div class="line"><a id="l00411" name="l00411"></a><span class="lineno">  411</span><span class="comment">   *</span></div>
<div class="line"><a id="l00412" name="l00412"></a><span class="lineno">  412</span><span class="comment">   * @tparam T</span></div>
<div class="line"><a id="l00413" name="l00413"></a><span class="lineno">  413</span><span class="comment">   *         Object type.  See class doc header for discussion on appropriate properties of `T`.</span></div>
<div class="line"><a id="l00414" name="l00414"></a><span class="lineno">  414</span><span class="comment">   *         Short version: PODs work; STL nested container+POD combos work, as long as</span></div>
<div class="line"><a id="l00415" name="l00415"></a><span class="lineno">  415</span><span class="comment">   *         a shm::stl allocator is used at all levels; manually-implemented non-STL-compliant data</span></div>
<div class="line"><a id="l00416" name="l00416"></a><span class="lineno">  416</span><span class="comment">   *         structures work if care is taken to use allocate() and #Pointer.</span></div>
<div class="line"><a id="l00417" name="l00417"></a><span class="lineno">  417</span><span class="comment">   * @tparam Ctor_args</span></div>
<div class="line"><a id="l00418" name="l00418"></a><span class="lineno">  418</span><span class="comment">   *         `T` ctor arg types.</span></div>
<div class="line"><a id="l00419" name="l00419"></a><span class="lineno">  419</span><span class="comment">   * @param ctor_args</span></div>
<div class="line"><a id="l00420" name="l00420"></a><span class="lineno">  420</span><span class="comment">   *        0 or more args to `T` constructor.</span></div>
<div class="line"><a id="l00421" name="l00421"></a><span class="lineno">  421</span><span class="comment">   * @return Non-null on success; `null` if ctor failed to attach a pool.</span></div>
<div class="line"><a id="l00422" name="l00422"></a><span class="lineno">  422</span><span class="comment">   */</span></div>
<div class="line"><a id="l00423" name="l00423"></a><span class="lineno">  423</span>  <span class="keyword">template</span>&lt;<span class="keyword">typename</span> T, <span class="keyword">typename</span>... Ctor_args&gt;</div>
<div class="line"><a id="l00424" name="l00424"></a><span class="lineno">  424</span>  Handle&lt;T&gt; <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#ab9f7ea056a55183d00dcbce573afcf36">construct</a>(Ctor_args&amp;&amp;... ctor_args);</div>
<div class="line"><a id="l00425" name="l00425"></a><span class="lineno">  425</span><span class="comment"></span> </div>
<div class="line"><a id="l00426" name="l00426"></a><span class="lineno">  426</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00427" name="l00427"></a><span class="lineno">  427</span><span class="comment">   * Adds an owner process to the owner count of the given construct()-created handle, and returns</span></div>
<div class="line"><a id="l00428" name="l00428"></a><span class="lineno">  428</span><span class="comment">   * an opaque blob, such that if one passes it to borrow_object() in the receiving process, that borrow_object()</span></div>
<div class="line"><a id="l00429" name="l00429"></a><span class="lineno">  429</span><span class="comment">   * shall return an equivalent #Handle in that process.  The returned `Blob` is guaranteed to have non-zero</span></div>
<div class="line"><a id="l00430" name="l00430"></a><span class="lineno">  430</span><span class="comment">   * size that is small enough to be considered very cheap to copy; in particular internally as of this writing</span></div>
<div class="line"><a id="l00431" name="l00431"></a><span class="lineno">  431</span><span class="comment">   * it is a `ptrdiff_t`.  Returns `.empty()` object if no pool attached to `*this`.</span></div>
<div class="line"><a id="l00432" name="l00432"></a><span class="lineno">  432</span><span class="comment">   *</span></div>
<div class="line"><a id="l00433" name="l00433"></a><span class="lineno">  433</span><span class="comment">   * It is the user&#39;s responsibility to transmit the returned blob, such as via a transport::Channel or any other</span></div>
<div class="line"><a id="l00434" name="l00434"></a><span class="lineno">  434</span><span class="comment">   * copying IPC mechanism, to the borrowing process and there pass it to `x-&gt;borrow_object()` (where `x`</span></div>
<div class="line"><a id="l00435" name="l00435"></a><span class="lineno">  435</span><span class="comment">   * is a Pool_arena accessing the same-named SHM pool as `*this`).  Failing to do so will leak the object until</span></div>
<div class="line"><a id="l00436" name="l00436"></a><span class="lineno">  436</span><span class="comment">   * remove_persistent().  That borrowing process dying without running #Handle dtor(s) on #Handle returned</span></div>
<div class="line"><a id="l00437" name="l00437"></a><span class="lineno">  437</span><span class="comment">   * by `x` borrow_object() will similarly leak it until remove_persistent().</span></div>
<div class="line"><a id="l00438" name="l00438"></a><span class="lineno">  438</span><span class="comment">   *</span></div>
<div class="line"><a id="l00439" name="l00439"></a><span class="lineno">  439</span><span class="comment">   * @tparam T</span></div>
<div class="line"><a id="l00440" name="l00440"></a><span class="lineno">  440</span><span class="comment">   *         See construct().</span></div>
<div class="line"><a id="l00441" name="l00441"></a><span class="lineno">  441</span><span class="comment">   * @param handle</span></div>
<div class="line"><a id="l00442" name="l00442"></a><span class="lineno">  442</span><span class="comment">   *        Value returned by construct() (lending from original allocating process) or borrow_object() (proxying); or</span></div>
<div class="line"><a id="l00443" name="l00443"></a><span class="lineno">  443</span><span class="comment">   *        copied/moved therefrom.  Note this is a mere `shared_ptr&lt;T&gt;` albeit with unspecified custom deleter</span></div>
<div class="line"><a id="l00444" name="l00444"></a><span class="lineno">  444</span><span class="comment">   *        logic attached.  See #Handle doc header.</span></div>
<div class="line"><a id="l00445" name="l00445"></a><span class="lineno">  445</span><span class="comment">   * @return See above.  `.empty()` if and only if ctor failed to attach a pool.</span></div>
<div class="line"><a id="l00446" name="l00446"></a><span class="lineno">  446</span><span class="comment">   */</span></div>
<div class="line"><a id="l00447" name="l00447"></a><span class="lineno">  447</span>  <span class="keyword">template</span>&lt;<span class="keyword">typename</span> T&gt;</div>
<div class="line"><a id="l00448" name="l00448"></a><span class="lineno">  448</span>  <a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a72867ce6e363dbc1ab1666768d8a7a09">Blob</a> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#acb300e64f92ab0aa5b70f8313c79a899">lend_object</a>(<span class="keyword">const</span> Handle&lt;T&gt;&amp; handle);</div>
<div class="line"><a id="l00449" name="l00449"></a><span class="lineno">  449</span><span class="comment"></span> </div>
<div class="line"><a id="l00450" name="l00450"></a><span class="lineno">  450</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00451" name="l00451"></a><span class="lineno">  451</span><span class="comment">   * Completes the cross-process operation begun by lend_object() that returned `serialization`; to be invoked in the</span></div>
<div class="line"><a id="l00452" name="l00452"></a><span class="lineno">  452</span><span class="comment">   * intended new owner process.  Returns null if no pool attached to `*this`.</span></div>
<div class="line"><a id="l00453" name="l00453"></a><span class="lineno">  453</span><span class="comment">   *</span></div>
<div class="line"><a id="l00454" name="l00454"></a><span class="lineno">  454</span><span class="comment">   * Consider the only 2 ways a user may obtain a new #Handle to a `T` from `*this`:</span></div>
<div class="line"><a id="l00455" name="l00455"></a><span class="lineno">  455</span><span class="comment">   *   - construct(): This is allocation by the original/first owner of the `T`.</span></div>
<div class="line"><a id="l00456" name="l00456"></a><span class="lineno">  456</span><span class="comment">   *   - borrow_object(), after lend_object() was called on a previous #Handle in another process, acquired *there*</span></div>
<div class="line"><a id="l00457" name="l00457"></a><span class="lineno">  457</span><span class="comment">   *     however it was acquired:</span></div>
<div class="line"><a id="l00458" name="l00458"></a><span class="lineno">  458</span><span class="comment">   *     - Acquired via construct(): I.e., the original/first owner lent to us.  I.e., it&#39;s the original loan.</span></div>
<div class="line"><a id="l00459" name="l00459"></a><span class="lineno">  459</span><span class="comment">   *     - Acquired via another borrow_object(): I.e., it was itself first borrowed from another.  I.e., it&#39;s a loan</span></div>
<div class="line"><a id="l00460" name="l00460"></a><span class="lineno">  460</span><span class="comment">   *       by a lender a/k/a *proxying*.</span></div>
<div class="line"><a id="l00461" name="l00461"></a><span class="lineno">  461</span><span class="comment">   *</span></div>
<div class="line"><a id="l00462" name="l00462"></a><span class="lineno">  462</span><span class="comment">   * ### Integration with shm::stl::Stateless_allocator ###</span></div>
<div class="line"><a id="l00463" name="l00463"></a><span class="lineno">  463</span><span class="comment">   * Crucially, the 2nd paragraph of similarly named section of construct() doc header -- where it speaks of</span></div>
<div class="line"><a id="l00464" name="l00464"></a><span class="lineno">  464</span><span class="comment">   * applying `Stateless_allocator` context around dtor call possibly invoked by returned handle&#39;s deleter --</span></div>
<div class="line"><a id="l00465" name="l00465"></a><span class="lineno">  465</span><span class="comment">   * applies exactly equally here.  Please read it.</span></div>
<div class="line"><a id="l00466" name="l00466"></a><span class="lineno">  466</span><span class="comment">   *</span></div>
<div class="line"><a id="l00467" name="l00467"></a><span class="lineno">  467</span><span class="comment">   * @tparam T</span></div>
<div class="line"><a id="l00468" name="l00468"></a><span class="lineno">  468</span><span class="comment">   *         See lend_object().</span></div>
<div class="line"><a id="l00469" name="l00469"></a><span class="lineno">  469</span><span class="comment">   * @param serialization</span></div>
<div class="line"><a id="l00470" name="l00470"></a><span class="lineno">  470</span><span class="comment">   *        Value, not `.empty()`, returned by lend_object() and transmitted bit-for-bit to this process.</span></div>
<div class="line"><a id="l00471" name="l00471"></a><span class="lineno">  471</span><span class="comment">   * @return Non-null on success; `null` if ctor failed to attach a pool.</span></div>
<div class="line"><a id="l00472" name="l00472"></a><span class="lineno">  472</span><span class="comment">   */</span></div>
<div class="line"><a id="l00473" name="l00473"></a><span class="lineno">  473</span>  <span class="keyword">template</span>&lt;<span class="keyword">typename</span> T&gt;</div>
<div class="line"><a id="l00474" name="l00474"></a><span class="lineno">  474</span>  Handle&lt;T&gt; <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#ad2f2b767d7da42e7e57592cc029386e5">borrow_object</a>(<span class="keyword">const</span> <a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a72867ce6e363dbc1ab1666768d8a7a09">Blob</a>&amp; serialization);</div>
<div class="line"><a id="l00475" name="l00475"></a><span class="lineno">  475</span><span class="comment"></span> </div>
<div class="line"><a id="l00476" name="l00476"></a><span class="lineno">  476</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00477" name="l00477"></a><span class="lineno">  477</span><span class="comment">   * Returns `true` if and only if `handle` came from either `this-&gt;construct&lt;T&gt;()` or `this-&gt;borrow_object&lt;T&gt;()`.</span></div>
<div class="line"><a id="l00478" name="l00478"></a><span class="lineno">  478</span><span class="comment">   * Another way of saying that is: if and only if `handle` may be passed to `this-&gt;lend_object&lt;T&gt;()`.</span></div>
<div class="line"><a id="l00479" name="l00479"></a><span class="lineno">  479</span><span class="comment">   * (The words &quot;came from&quot; mean &quot;was returned by or is a copy/move of one that was,&quot; or</span></div>
<div class="line"><a id="l00480" name="l00480"></a><span class="lineno">  480</span><span class="comment">   * equivalently &quot;belongs to the `shared_ptr` group of one that was returned by.&quot;)</span></div>
<div class="line"><a id="l00481" name="l00481"></a><span class="lineno">  481</span><span class="comment">   *</span></div>
<div class="line"><a id="l00482" name="l00482"></a><span class="lineno">  482</span><span class="comment">   * @param handle</span></div>
<div class="line"><a id="l00483" name="l00483"></a><span class="lineno">  483</span><span class="comment">   *        An object, or copy/move of an object, returned by `construct&lt;T&gt;()` or `borrow_object&lt;T&gt;()`</span></div>
<div class="line"><a id="l00484" name="l00484"></a><span class="lineno">  484</span><span class="comment">   *        of *a* Pool_arena (not necessarily `*this`), while `*this` was already constructed.</span></div>
<div class="line"><a id="l00485" name="l00485"></a><span class="lineno">  485</span><span class="comment">   * @return See above.</span></div>
<div class="line"><a id="l00486" name="l00486"></a><span class="lineno">  486</span><span class="comment">   */</span></div>
<div class="line"><a id="l00487" name="l00487"></a><span class="lineno">  487</span>  <span class="keyword">template</span>&lt;<span class="keyword">typename</span> T&gt;</div>
<div class="line"><a id="l00488" name="l00488"></a><span class="lineno">  488</span>  <span class="keywordtype">bool</span> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#ad2d54cc87b56613bba32aabd2c52ef13">is_handle_in_arena</a>(<span class="keyword">const</span> Handle&lt;T&gt;&amp; handle) <span class="keyword">const</span>;</div>
<div class="line"><a id="l00489" name="l00489"></a><span class="lineno">  489</span> </div>
<div class="line"><a id="l00490" name="l00490"></a><span class="lineno">  490</span>  <span class="comment">// Data.</span></div>
<div class="line"><a id="l00491" name="l00491"></a><span class="lineno">  491</span><span class="comment"></span> </div>
<div class="line"><a id="l00492" name="l00492"></a><span class="lineno">  492</span><span class="comment">  /// SHM pool name as set immutably at construction.</span></div>
<div class="line"><a id="l00493" name="l00493"></a><span class="lineno"><a class="line" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a71009bb725b4cd68bea4ac99fa81ee2e">  493</a></span><span class="comment"></span>  <span class="keyword">const</span> <a class="code hl_class" href="classipc_1_1util_1_1Shared__name.html">Shared_name</a> <a class="code hl_variable" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a71009bb725b4cd68bea4ac99fa81ee2e">m_pool_name</a>;</div>
<div class="line"><a id="l00494" name="l00494"></a><span class="lineno">  494</span> </div>
<div class="line"><a id="l00495" name="l00495"></a><span class="lineno">  495</span><span class="keyword">private</span>:</div>
<div class="line"><a id="l00496" name="l00496"></a><span class="lineno">  496</span>  <span class="comment">// Types.</span></div>
<div class="line"><a id="l00497" name="l00497"></a><span class="lineno">  497</span><span class="comment"></span> </div>
<div class="line"><a id="l00498" name="l00498"></a><span class="lineno">  498</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00499" name="l00499"></a><span class="lineno">  499</span><span class="comment">   * The SHM pool type one instance of which is managed by `*this`.</span></div>
<div class="line"><a id="l00500" name="l00500"></a><span class="lineno">  500</span><span class="comment">   * It would be possible to parameterize this somewhat further, such as specifying different allocation algorithms</span></div>
<div class="line"><a id="l00501" name="l00501"></a><span class="lineno">  501</span><span class="comment">   * or speed up perf in single-thread situations.  See class doc header for discussion.  It is not a formal</span></div>
<div class="line"><a id="l00502" name="l00502"></a><span class="lineno">  502</span><span class="comment">   * to-do yet.</span></div>
<div class="line"><a id="l00503" name="l00503"></a><span class="lineno">  503</span><span class="comment">   *</span></div>
<div class="line"><a id="l00504" name="l00504"></a><span class="lineno">  504</span><span class="comment">   * We *do* specify it as `basic_managed_shared_memory` with explicit template-parameters, as opposed to the more</span></div>
<div class="line"><a id="l00505" name="l00505"></a><span class="lineno">  505</span><span class="comment">   * common `managed_shared_memory` alias, as of this writing because we don&#39;t need an index (by-name construction</span></div>
<div class="line"><a id="l00506" name="l00506"></a><span class="lineno">  506</span><span class="comment">   * and lookup of objects), so we specify `null_index` to avoid wasting space on it.  (So then we must specify the</span></div>
<div class="line"><a id="l00507" name="l00507"></a><span class="lineno">  507</span><span class="comment">   * other params explicitly.)</span></div>
<div class="line"><a id="l00508" name="l00508"></a><span class="lineno">  508</span><span class="comment">   */</span></div>
<div class="line"><a id="l00509" name="l00509"></a><span class="lineno"><a class="line" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a5914c3039a00fa0396f34e9b357934a4">  509</a></span>  <span class="keyword">using </span><a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a5914c3039a00fa0396f34e9b357934a4">Pool</a> = ::ipc::bipc::basic_managed_shared_memory&lt;char,</div>
<div class="line"><a id="l00510" name="l00510"></a><span class="lineno">  510</span>                                                        ::ipc::bipc::rbtree_best_fit&lt;::ipc::bipc::mutex_family&gt;,</div>
<div class="line"><a id="l00511" name="l00511"></a><span class="lineno">  511</span>                                                        ::ipc::bipc::null_index&gt;;</div>
<div class="line"><a id="l00512" name="l00512"></a><span class="lineno">  512</span><span class="comment"></span> </div>
<div class="line"><a id="l00513" name="l00513"></a><span class="lineno">  513</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00514" name="l00514"></a><span class="lineno">  514</span><span class="comment">   * The data structure stored in SHM corresponding to an original construct()-returned #Handle;</span></div>
<div class="line"><a id="l00515" name="l00515"></a><span class="lineno">  515</span><span class="comment">   * exactly one of which exists per construct() call invoked from any Pool_arena connected to the underlying pool.</span></div>
<div class="line"><a id="l00516" name="l00516"></a><span class="lineno">  516</span><span class="comment">   * It is created in construct() and placed in the SHM pool.  It is destroyed once its #m_atomic_owner_ct</span></div>
<div class="line"><a id="l00517" name="l00517"></a><span class="lineno">  517</span><span class="comment">   * reaches 0, which occurs once the last process for which a #Handle (`shared_ptr`) group ref-count reaches 0</span></div>
<div class="line"><a id="l00518" name="l00518"></a><span class="lineno">  518</span><span class="comment">   * detects this fact in its custom deleter and internally invokes deallocate() for the buffer,</span></div>
<div class="line"><a id="l00519" name="l00519"></a><span class="lineno">  519</span><span class="comment">   * wherein the Handle_in_shm resides.</span></div>
<div class="line"><a id="l00520" name="l00520"></a><span class="lineno">  520</span><span class="comment">   *</span></div>
<div class="line"><a id="l00521" name="l00521"></a><span class="lineno">  521</span><span class="comment">   * @tparam T</span></div>
<div class="line"><a id="l00522" name="l00522"></a><span class="lineno">  522</span><span class="comment">   *         The `T` from the associated #Handle.</span></div>
<div class="line"><a id="l00523" name="l00523"></a><span class="lineno">  523</span><span class="comment">   */</span></div>
<div class="line"><a id="l00524" name="l00524"></a><span class="lineno">  524</span>  <span class="keyword">template</span>&lt;<span class="keyword">typename</span> T&gt;</div>
<div class="line"><a id="l00525" name="l00525"></a><span class="lineno"><a class="line" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html">  525</a></span>  <span class="keyword">struct </span><a class="code hl_struct" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html">Handle_in_shm</a></div>
<div class="line"><a id="l00526" name="l00526"></a><span class="lineno">  526</span>  {</div>
<div class="line"><a id="l00527" name="l00527"></a><span class="lineno">  527</span>    <span class="comment">// Types.</span></div>
<div class="line"><a id="l00528" name="l00528"></a><span class="lineno">  528</span><span class="comment"></span> </div>
<div class="line"><a id="l00529" name="l00529"></a><span class="lineno">  529</span><span class="comment">    /**</span></div>
<div class="line"><a id="l00530" name="l00530"></a><span class="lineno">  530</span><span class="comment">     * Atomically accessed count of each time the following events occurs for a given Handle_in_shm in</span></div>
<div class="line"><a id="l00531" name="l00531"></a><span class="lineno">  531</span><span class="comment">     * the backing pool:</span></div>
<div class="line"><a id="l00532" name="l00532"></a><span class="lineno">  532</span><span class="comment">     *   - initial construction via construct(), which returns the original #Handle and creates</span></div>
<div class="line"><a id="l00533" name="l00533"></a><span class="lineno">  533</span><span class="comment">     *     the Handle_in_shm;</span></div>
<div class="line"><a id="l00534" name="l00534"></a><span class="lineno">  534</span><span class="comment">     *   - each call to lend_object() on that #Handle (internally, on the associated Handle_in_shm);</span></div>
<div class="line"><a id="l00535" name="l00535"></a><span class="lineno">  535</span><span class="comment">     *   - *minus* any corresponding invocations of the #Handle custom deleter.</span></div>
<div class="line"><a id="l00536" name="l00536"></a><span class="lineno">  536</span><span class="comment">     */</span></div>
<div class="line"><a id="l00537" name="l00537"></a><span class="lineno"><a class="line" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html#aef706713d40d801d0cb213e08201c571">  537</a></span>    <span class="keyword">using </span><a class="code hl_typedef" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html#aef706713d40d801d0cb213e08201c571">Atomic_owner_ct</a> = std::atomic&lt;unsigned int&gt;;</div>
<div class="line"><a id="l00538" name="l00538"></a><span class="lineno">  538</span> </div>
<div class="line"><a id="l00539" name="l00539"></a><span class="lineno">  539</span>    <span class="comment">// Data.</span></div>
<div class="line"><a id="l00540" name="l00540"></a><span class="lineno">  540</span><span class="comment"></span> </div>
<div class="line"><a id="l00541" name="l00541"></a><span class="lineno">  541</span><span class="comment">    /**</span></div>
<div class="line"><a id="l00542" name="l00542"></a><span class="lineno">  542</span><span class="comment">     * The constructed object; `Handle::get()` returns `&amp;m_obj`.  This must be the first member in</span></div>
<div class="line"><a id="l00543" name="l00543"></a><span class="lineno">  543</span><span class="comment">     * Handle_in_shm, because the custom deleter `reinterpret_cast`s `Handle::get()` to mean `Handle_in_shm*`.</span></div>
<div class="line"><a id="l00544" name="l00544"></a><span class="lineno">  544</span><span class="comment">     * If this arrangement is modified, one would need to use `offsetof` (or something) as well.</span></div>
<div class="line"><a id="l00545" name="l00545"></a><span class="lineno">  545</span><span class="comment">     */</span></div>
<div class="line"><a id="l00546" name="l00546"></a><span class="lineno"><a class="line" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html#ac787f6c20943bc76027cf25c7548d797">  546</a></span>    T <a class="code hl_variable" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html#ac787f6c20943bc76027cf25c7548d797">m_obj</a>;</div>
<div class="line"><a id="l00547" name="l00547"></a><span class="lineno">  547</span><span class="comment"></span> </div>
<div class="line"><a id="l00548" name="l00548"></a><span class="lineno">  548</span><span class="comment">    /// See #Atomic_owner_ct doc header.  This value is 1+; once it reaches 0 `*this` is destroyed in SHM.</span></div>
<div class="line"><a id="l00549" name="l00549"></a><span class="lineno"><a class="line" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html#aa801c3aa3c8f15945c5ac94936bd072d">  549</a></span><span class="comment"></span>    <a class="code hl_typedef" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html#aef706713d40d801d0cb213e08201c571">Atomic_owner_ct</a> <a class="code hl_variable" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html#aa801c3aa3c8f15945c5ac94936bd072d">m_atomic_owner_ct</a>;</div>
<div class="line"><a id="l00550" name="l00550"></a><span class="lineno">  550</span>  }; <span class="comment">// struct Handle_in_shm</span></div>
<div class="line"><a id="l00551" name="l00551"></a><span class="lineno">  551</span> </div>
<div class="line"><a id="l00552" name="l00552"></a><span class="lineno">  552</span>  <span class="comment">// Constructors.</span></div>
<div class="line"><a id="l00553" name="l00553"></a><span class="lineno">  553</span><span class="comment"></span> </div>
<div class="line"><a id="l00554" name="l00554"></a><span class="lineno">  554</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00555" name="l00555"></a><span class="lineno">  555</span><span class="comment">   * Helper ctor delegated by the 2 `public` ctors that take `Open_or_create` or `Create_only` mode.</span></div>
<div class="line"><a id="l00556" name="l00556"></a><span class="lineno">  556</span><span class="comment">   *</span></div>
<div class="line"><a id="l00557" name="l00557"></a><span class="lineno">  557</span><span class="comment">   * @tparam Mode_tag</span></div>
<div class="line"><a id="l00558" name="l00558"></a><span class="lineno">  558</span><span class="comment">   *         Either util::Open_or_create or util::Create_only.</span></div>
<div class="line"><a id="l00559" name="l00559"></a><span class="lineno">  559</span><span class="comment">   * @param logger_ptr</span></div>
<div class="line"><a id="l00560" name="l00560"></a><span class="lineno">  560</span><span class="comment">   *        See `public` ctors.</span></div>
<div class="line"><a id="l00561" name="l00561"></a><span class="lineno">  561</span><span class="comment">   * @param pool_name</span></div>
<div class="line"><a id="l00562" name="l00562"></a><span class="lineno">  562</span><span class="comment">   *        See `public` ctors.</span></div>
<div class="line"><a id="l00563" name="l00563"></a><span class="lineno">  563</span><span class="comment">   * @param mode_tag</span></div>
<div class="line"><a id="l00564" name="l00564"></a><span class="lineno">  564</span><span class="comment">   *        See `public` ctors.</span></div>
<div class="line"><a id="l00565" name="l00565"></a><span class="lineno">  565</span><span class="comment">   * @param pool_sz</span></div>
<div class="line"><a id="l00566" name="l00566"></a><span class="lineno">  566</span><span class="comment">   *        See `public` ctors.</span></div>
<div class="line"><a id="l00567" name="l00567"></a><span class="lineno">  567</span><span class="comment">   * @param perms</span></div>
<div class="line"><a id="l00568" name="l00568"></a><span class="lineno">  568</span><span class="comment">   *        See `public` ctors.</span></div>
<div class="line"><a id="l00569" name="l00569"></a><span class="lineno">  569</span><span class="comment">   * @param err_code</span></div>
<div class="line"><a id="l00570" name="l00570"></a><span class="lineno">  570</span><span class="comment">   *        See `public` ctors.</span></div>
<div class="line"><a id="l00571" name="l00571"></a><span class="lineno">  571</span><span class="comment">   */</span></div>
<div class="line"><a id="l00572" name="l00572"></a><span class="lineno">  572</span>  <span class="keyword">template</span>&lt;<span class="keyword">typename</span> Mode_tag&gt;</div>
<div class="line"><a id="l00573" name="l00573"></a><span class="lineno">  573</span>  <span class="keyword">explicit</span> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a77acacecacdd45514ebf9db99b4ab4c3">Pool_arena</a>(Mode_tag mode_tag, flow::log::Logger* logger_ptr, <span class="keyword">const</span> <a class="code hl_class" href="classipc_1_1util_1_1Shared__name.html">Shared_name</a>&amp; pool_name, <span class="keywordtype">size_t</span> pool_sz,</div>
<div class="line"><a id="l00574" name="l00574"></a><span class="lineno">  574</span>                      <span class="keyword">const</span> <a class="code hl_typedef" href="namespaceipc_1_1util.html#a1b398ae730d1e6040687cb2397115152">util::Permissions</a>&amp; perms, <a class="code hl_typedef" href="namespaceipc.html#aa3192e586cc45d3e7c22463bf2760f89">Error_code</a>* err_code);</div>
<div class="line"><a id="l00575" name="l00575"></a><span class="lineno">  575</span> </div>
<div class="line"><a id="l00576" name="l00576"></a><span class="lineno">  576</span>  <span class="comment">// Methods.</span></div>
<div class="line"><a id="l00577" name="l00577"></a><span class="lineno">  577</span><span class="comment"></span> </div>
<div class="line"><a id="l00578" name="l00578"></a><span class="lineno">  578</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00579" name="l00579"></a><span class="lineno">  579</span><span class="comment">   * `std::construct_at()` equivalent; unavailable until C++20, so here it is.</span></div>
<div class="line"><a id="l00580" name="l00580"></a><span class="lineno">  580</span><span class="comment">   *</span></div>
<div class="line"><a id="l00581" name="l00581"></a><span class="lineno">  581</span><span class="comment">   * @tparam T</span></div>
<div class="line"><a id="l00582" name="l00582"></a><span class="lineno">  582</span><span class="comment">   *         Object type.</span></div>
<div class="line"><a id="l00583" name="l00583"></a><span class="lineno">  583</span><span class="comment">   * @tparam Ctor_args</span></div>
<div class="line"><a id="l00584" name="l00584"></a><span class="lineno">  584</span><span class="comment">   *         `T` ctor arg types.</span></div>
<div class="line"><a id="l00585" name="l00585"></a><span class="lineno">  585</span><span class="comment">   * @param obj</span></div>
<div class="line"><a id="l00586" name="l00586"></a><span class="lineno">  586</span><span class="comment">   *        Pointer to uninitialized `T`.</span></div>
<div class="line"><a id="l00587" name="l00587"></a><span class="lineno">  587</span><span class="comment">   * @param ctor_args</span></div>
<div class="line"><a id="l00588" name="l00588"></a><span class="lineno">  588</span><span class="comment">   *        Ctor args for `T::T()`.</span></div>
<div class="line"><a id="l00589" name="l00589"></a><span class="lineno">  589</span><span class="comment">   */</span></div>
<div class="line"><a id="l00590" name="l00590"></a><span class="lineno">  590</span>  <span class="keyword">template</span>&lt;<span class="keyword">typename</span> T, <span class="keyword">typename</span>... Ctor_args&gt;</div>
<div class="line"><a id="l00591" name="l00591"></a><span class="lineno">  591</span>  <span class="keyword">static</span> <span class="keywordtype">void</span> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a2823d6522e276e7b7b5bd518327b85d6">construct_at</a>(T* obj, Ctor_args&amp;&amp;... ctor_args);</div>
<div class="line"><a id="l00592" name="l00592"></a><span class="lineno">  592</span><span class="comment"></span> </div>
<div class="line"><a id="l00593" name="l00593"></a><span class="lineno">  593</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00594" name="l00594"></a><span class="lineno">  594</span><span class="comment">   * Identical deleter for #Handle returned by both construct() and borrow_object(); invoked when a given process&#39;s</span></div>
<div class="line"><a id="l00595" name="l00595"></a><span class="lineno">  595</span><span class="comment">   * (borrow_object() caller&#39;s) `shared_ptr` group reaches ref-count 0.  It decrements Handle_in_shm::m_atomic_owner_ct;</span></div>
<div class="line"><a id="l00596" name="l00596"></a><span class="lineno">  596</span><span class="comment">   * and if and only if that made it reach zero performs the opposite of what construct() did including:</span></div>
<div class="line"><a id="l00597" name="l00597"></a><span class="lineno">  597</span><span class="comment">   *   - runs `T::~T()` dtor;</span></div>
<div class="line"><a id="l00598" name="l00598"></a><span class="lineno">  598</span><span class="comment">   *   - deallocate().</span></div>
<div class="line"><a id="l00599" name="l00599"></a><span class="lineno">  599</span><span class="comment">   *</span></div>
<div class="line"><a id="l00600" name="l00600"></a><span class="lineno">  600</span><span class="comment">   * Otherwise (if `m_atomic_owner_ct` is not yet 0) does nothing further; other owners still remain.</span></div>
<div class="line"><a id="l00601" name="l00601"></a><span class="lineno">  601</span><span class="comment">   *</span></div>
<div class="line"><a id="l00602" name="l00602"></a><span class="lineno">  602</span><span class="comment">   * @param handle_state</span></div>
<div class="line"><a id="l00603" name="l00603"></a><span class="lineno">  603</span><span class="comment">   *        `Handle&lt;T&gt;::~Handle()` shall run, and if that made shared-ref-count reach 0, call</span></div>
<div class="line"><a id="l00604" name="l00604"></a><span class="lineno">  604</span><span class="comment">   *        `handle_deleter_impl(...that_ptr...)`.  Since the #Handle returned by construct() and borrow_object()</span></div>
<div class="line"><a id="l00605" name="l00605"></a><span class="lineno">  605</span><span class="comment">   *        is really an alias-cted `shared_ptr&lt;T&gt;` to `shared_ptr&lt;Handle_in_shm&lt;T&gt;&gt;`, and Handle_in_shm::m_obj</span></div>
<div class="line"><a id="l00606" name="l00606"></a><span class="lineno">  606</span><span class="comment">   *        (of type `T`) is the first member in its type, those addresses are numerically equal.</span></div>
<div class="line"><a id="l00607" name="l00607"></a><span class="lineno">  607</span><span class="comment">   */</span></div>
<div class="line"><a id="l00608" name="l00608"></a><span class="lineno">  608</span>  <span class="keyword">template</span>&lt;<span class="keyword">typename</span> T&gt;</div>
<div class="line"><a id="l00609" name="l00609"></a><span class="lineno">  609</span>  <span class="keywordtype">void</span> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#ade690ffcab383978303f974e889deb54">handle_deleter_impl</a>(<a class="code hl_struct" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html">Handle_in_shm&lt;T&gt;</a>* handle_state);</div>
<div class="line"><a id="l00610" name="l00610"></a><span class="lineno">  610</span> </div>
<div class="line"><a id="l00611" name="l00611"></a><span class="lineno">  611</span>  <span class="comment">// Data.</span></div>
<div class="line"><a id="l00612" name="l00612"></a><span class="lineno">  612</span><span class="comment"></span> </div>
<div class="line"><a id="l00613" name="l00613"></a><span class="lineno">  613</span><span class="comment">  /// Attached SHM pool.  If ctor fails in non-throwing fashion then this remains null.  Immutable after ctor.</span></div>
<div class="line"><a id="l00614" name="l00614"></a><span class="lineno"><a class="line" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a308351dc72f76407cf845af163fa0124">  614</a></span><span class="comment"></span>  std::optional&lt;Pool&gt; <a class="code hl_variable" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a308351dc72f76407cf845af163fa0124">m_pool</a>;</div>
<div class="line"><a id="l00615" name="l00615"></a><span class="lineno">  615</span>}; <span class="comment">// class Pool_arena</span></div>
<div class="line"><a id="l00616" name="l00616"></a><span class="lineno">  616</span> </div>
<div class="line"><a id="l00617" name="l00617"></a><span class="lineno">  617</span><span class="comment">// Free functions: in *_fwd.hpp.</span></div>
<div class="line"><a id="l00618" name="l00618"></a><span class="lineno">  618</span> </div>
<div class="line"><a id="l00619" name="l00619"></a><span class="lineno">  619</span><span class="comment">// Template implementations.</span></div>
<div class="line"><a id="l00620" name="l00620"></a><span class="lineno">  620</span> </div>
<div class="line"><a id="l00621" name="l00621"></a><span class="lineno">  621</span><span class="keyword">template</span>&lt;<span class="keyword">typename</span> T&gt;</div>
<div class="line"><a id="l00622" name="l00622"></a><span class="lineno"><a class="line" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#ad2d54cc87b56613bba32aabd2c52ef13">  622</a></span><span class="keywordtype">bool</span> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#ad2d54cc87b56613bba32aabd2c52ef13">Pool_arena::is_handle_in_arena</a>(<span class="keyword">const</span> <a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a662a55c9ba6eb5c389ddf9780ee801cb">Handle&lt;T&gt;</a>&amp; handle)<span class="keyword"> const</span></div>
<div class="line"><a id="l00623" name="l00623"></a><span class="lineno">  623</span><span class="keyword"></span>{</div>
<div class="line"><a id="l00624" name="l00624"></a><span class="lineno">  624</span>  <span class="keyword">const</span> <span class="keyword">auto</span> p = <span class="keyword">reinterpret_cast&lt;</span><span class="keyword">const </span>uint8_t*<span class="keyword">&gt;</span>(handle.get());</div>
<div class="line"><a id="l00625" name="l00625"></a><span class="lineno">  625</span>  <span class="keyword">const</span> <span class="keyword">auto</span> pool_base = <span class="keyword">static_cast&lt;</span><span class="keyword">const </span>uint8_t*<span class="keyword">&gt;</span>(<a class="code hl_variable" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a308351dc72f76407cf845af163fa0124">m_pool</a>-&gt;get_address());</div>
<div class="line"><a id="l00626" name="l00626"></a><span class="lineno">  626</span>  <span class="keywordflow">return</span> (p &gt;= pool_base) &amp;&amp; (p &lt; (pool_base + <a class="code hl_variable" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a308351dc72f76407cf845af163fa0124">m_pool</a>-&gt;get_size()));</div>
<div class="line"><a id="l00627" name="l00627"></a><span class="lineno">  627</span>}</div>
<div class="line"><a id="l00628" name="l00628"></a><span class="lineno">  628</span> </div>
<div class="line"><a id="l00629" name="l00629"></a><span class="lineno">  629</span><span class="keyword">template</span>&lt;<span class="keyword">typename</span> T, <span class="keyword">typename</span>... Ctor_args&gt;</div>
<div class="line"><a id="l00630" name="l00630"></a><span class="lineno"><a class="line" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#ab9f7ea056a55183d00dcbce573afcf36">  630</a></span><a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a662a55c9ba6eb5c389ddf9780ee801cb">Pool_arena::Handle&lt;T&gt;</a> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#ab9f7ea056a55183d00dcbce573afcf36">Pool_arena::construct</a>(Ctor_args&amp;&amp;... ctor_args)</div>
<div class="line"><a id="l00631" name="l00631"></a><span class="lineno">  631</span>{</div>
<div class="line"><a id="l00632" name="l00632"></a><span class="lineno">  632</span>  <span class="keyword">using </span>Value = T;</div>
<div class="line"><a id="l00633" name="l00633"></a><span class="lineno">  633</span>  <span class="keyword">using </span>Shm_handle = <a class="code hl_struct" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html">Handle_in_shm&lt;Value&gt;</a>;</div>
<div class="line"><a id="l00634" name="l00634"></a><span class="lineno">  634</span>  <span class="keyword">using </span>boost::shared_ptr;</div>
<div class="line"><a id="l00635" name="l00635"></a><span class="lineno">  635</span> </div>
<div class="line"><a id="l00636" name="l00636"></a><span class="lineno">  636</span>  <span class="keywordflow">if</span> (!<a class="code hl_variable" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a308351dc72f76407cf845af163fa0124">m_pool</a>)</div>
<div class="line"><a id="l00637" name="l00637"></a><span class="lineno">  637</span>  {</div>
<div class="line"><a id="l00638" name="l00638"></a><span class="lineno">  638</span>    <span class="keywordflow">return</span> <a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a662a55c9ba6eb5c389ddf9780ee801cb">Handle&lt;Value&gt;</a>{};</div>
<div class="line"><a id="l00639" name="l00639"></a><span class="lineno">  639</span>  }</div>
<div class="line"><a id="l00640" name="l00640"></a><span class="lineno">  640</span>  <span class="comment">// else</span></div>
<div class="line"><a id="l00641" name="l00641"></a><span class="lineno">  641</span> </div>
<div class="line"><a id="l00642" name="l00642"></a><span class="lineno">  642</span>  <span class="keyword">const</span> <span class="keyword">auto</span> handle_state = <span class="keyword">static_cast&lt;</span>Shm_handle*<span class="keyword">&gt;</span>(<a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a9da3a100a0b7199644edbadacc9083c9">allocate</a>(<span class="keyword">sizeof</span>(Shm_handle)));</div>
<div class="line"><a id="l00643" name="l00643"></a><span class="lineno">  643</span>  <span class="comment">// Buffer acquired but uninitialized.  Construct the owner count to 1 (just us: no lend_object() yet).</span></div>
<div class="line"><a id="l00644" name="l00644"></a><span class="lineno">  644</span>  <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a2823d6522e276e7b7b5bd518327b85d6">construct_at</a>(&amp;handle_state-&gt;m_atomic_owner_ct, 1);</div>
<div class="line"><a id="l00645" name="l00645"></a><span class="lineno">  645</span>  <span class="comment">// Construct the T itself.  As advertised try to help out by setting selves as the current arena.</span></div>
<div class="line"><a id="l00646" name="l00646"></a><span class="lineno">  646</span>  {</div>
<div class="line"><a id="l00647" name="l00647"></a><span class="lineno">  647</span>    <a class="code hl_class" href="classipc_1_1shm_1_1stl_1_1Arena__activator.html">Pool_arena_activator</a> ctx{<span class="keyword">this</span>};</div>
<div class="line"><a id="l00648" name="l00648"></a><span class="lineno">  648</span>    <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a2823d6522e276e7b7b5bd518327b85d6">construct_at</a>(&amp;handle_state-&gt;m_obj, std::forward&lt;Ctor_args&gt;(ctor_args)...);</div>
<div class="line"><a id="l00649" name="l00649"></a><span class="lineno">  649</span>  }</div>
<div class="line"><a id="l00650" name="l00650"></a><span class="lineno">  650</span> </div>
<div class="line"><a id="l00651" name="l00651"></a><span class="lineno">  651</span>  shared_ptr&lt;Shm_handle&gt; real_shm_handle{handle_state, [<span class="keyword">this</span>](Shm_handle* handle_state)</div>
<div class="line"><a id="l00652" name="l00652"></a><span class="lineno">  652</span>  {</div>
<div class="line"><a id="l00653" name="l00653"></a><span class="lineno">  653</span>    handle_deleter_impl&lt;Value&gt;(handle_state);</div>
<div class="line"><a id="l00654" name="l00654"></a><span class="lineno">  654</span>  }}; <span class="comment">// Custom deleter.</span></div>
<div class="line"><a id="l00655" name="l00655"></a><span class="lineno">  655</span> </div>
<div class="line"><a id="l00656" name="l00656"></a><span class="lineno">  656</span>  <span class="comment">// Return alias shared_ptr whose .get() gives &amp;m_obj but in reality aliases to real_shm_handle.</span></div>
<div class="line"><a id="l00657" name="l00657"></a><span class="lineno">  657</span>  <span class="keywordflow">return</span> <a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a662a55c9ba6eb5c389ddf9780ee801cb">Handle&lt;Value&gt;</a>{std::move(real_shm_handle), &amp;handle_state-&gt;m_obj};</div>
<div class="line"><a id="l00658" name="l00658"></a><span class="lineno">  658</span>} <span class="comment">// Pool_arena::construct()</span></div>
<div class="line"><a id="l00659" name="l00659"></a><span class="lineno">  659</span> </div>
<div class="line"><a id="l00660" name="l00660"></a><span class="lineno">  660</span><span class="keyword">template</span>&lt;<span class="keyword">typename</span> T&gt;</div>
<div class="line"><a id="l00661" name="l00661"></a><span class="lineno"><a class="line" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#acb300e64f92ab0aa5b70f8313c79a899">  661</a></span><a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a72867ce6e363dbc1ab1666768d8a7a09">Pool_arena::Blob</a> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#acb300e64f92ab0aa5b70f8313c79a899">Pool_arena::lend_object</a>(<span class="keyword">const</span> <a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a662a55c9ba6eb5c389ddf9780ee801cb">Handle&lt;T&gt;</a>&amp; handle)</div>
<div class="line"><a id="l00662" name="l00662"></a><span class="lineno">  662</span>{</div>
<div class="line"><a id="l00663" name="l00663"></a><span class="lineno">  663</span>  <span class="keyword">using </span>Value = T;</div>
<div class="line"><a id="l00664" name="l00664"></a><span class="lineno">  664</span>  <span class="keyword">using </span>Shm_handle = <a class="code hl_struct" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html">Handle_in_shm&lt;Value&gt;</a>;</div>
<div class="line"><a id="l00665" name="l00665"></a><span class="lineno">  665</span>  <span class="keyword">using </span><a class="code hl_typedef" href="namespaceipc_1_1util.html#ae0be7edba7e30ffa3f8b742af621f2ab">util::Blob_const</a>;</div>
<div class="line"><a id="l00666" name="l00666"></a><span class="lineno">  666</span>  <span class="keyword">using </span>flow::util::buffers_dump_string;</div>
<div class="line"><a id="l00667" name="l00667"></a><span class="lineno">  667</span> </div>
<div class="line"><a id="l00668" name="l00668"></a><span class="lineno">  668</span>  <span class="keywordflow">if</span> (!<a class="code hl_variable" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a308351dc72f76407cf845af163fa0124">m_pool</a>)</div>
<div class="line"><a id="l00669" name="l00669"></a><span class="lineno">  669</span>  {</div>
<div class="line"><a id="l00670" name="l00670"></a><span class="lineno">  670</span>    <span class="keywordflow">return</span> <a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a72867ce6e363dbc1ab1666768d8a7a09">Blob</a>{};</div>
<div class="line"><a id="l00671" name="l00671"></a><span class="lineno">  671</span>  }</div>
<div class="line"><a id="l00672" name="l00672"></a><span class="lineno">  672</span>  <span class="comment">// else</span></div>
<div class="line"><a id="l00673" name="l00673"></a><span class="lineno">  673</span> </div>
<div class="line"><a id="l00674" name="l00674"></a><span class="lineno">  674</span>  <span class="keyword">const</span> <span class="keyword">auto</span> handle_state = <span class="keyword">reinterpret_cast&lt;</span>Shm_handle*<span class="keyword">&gt;</span>(handle.get());</div>
<div class="line"><a id="l00675" name="l00675"></a><span class="lineno">  675</span>  <span class="keyword">const</span> <span class="keyword">auto</span> new_owner_ct = ++handle_state-&gt;<a class="code hl_variable" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html#aa801c3aa3c8f15945c5ac94936bd072d">m_atomic_owner_ct</a>;</div>
<div class="line"><a id="l00676" name="l00676"></a><span class="lineno">  676</span> </div>
<div class="line"><a id="l00677" name="l00677"></a><span class="lineno">  677</span>  <span class="keyword">const</span> ptrdiff_t offset_from_pool_base = <span class="keyword">reinterpret_cast&lt;</span><span class="keyword">const </span>uint8_t*<span class="keyword">&gt;</span>(handle_state)</div>
<div class="line"><a id="l00678" name="l00678"></a><span class="lineno">  678</span>                                          - <span class="keyword">static_cast&lt;</span><span class="keyword">const </span>uint8_t*<span class="keyword">&gt;</span>(<a class="code hl_variable" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a308351dc72f76407cf845af163fa0124">m_pool</a>-&gt;get_address());</div>
<div class="line"><a id="l00679" name="l00679"></a><span class="lineno">  679</span> </div>
<div class="line"><a id="l00680" name="l00680"></a><span class="lineno">  680</span>  <a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a72867ce6e363dbc1ab1666768d8a7a09">Blob</a> serialization{<span class="keyword">sizeof</span>(offset_from_pool_base)};</div>
<div class="line"><a id="l00681" name="l00681"></a><span class="lineno">  681</span>  *(<span class="keyword">reinterpret_cast&lt;</span>ptrdiff_t*<span class="keyword">&gt;</span>(serialization.data())) = offset_from_pool_base;</div>
<div class="line"><a id="l00682" name="l00682"></a><span class="lineno">  682</span> </div>
<div class="line"><a id="l00683" name="l00683"></a><span class="lineno">  683</span>  FLOW_LOG_TRACE(<span class="stringliteral">&quot;SHM-classic pool [&quot;</span> &lt;&lt; *<span class="keyword">this</span> &lt;&lt; <span class="stringliteral">&quot;]: Serializing SHM outer handle [&quot;</span> &lt;&lt; handle &lt;&lt; <span class="stringliteral">&quot;] before &quot;</span></div>
<div class="line"><a id="l00684" name="l00684"></a><span class="lineno">  684</span>                 <span class="stringliteral">&quot;IPC-transmission: Owning process-count incremented to [&quot;</span> &lt;&lt; new_owner_ct &lt;&lt; <span class="stringliteral">&quot;] &quot;</span></div>
<div class="line"><a id="l00685" name="l00685"></a><span class="lineno">  685</span>                 <span class="stringliteral">&quot;(may change concurrently).  &quot;</span></div>
<div class="line"><a id="l00686" name="l00686"></a><span class="lineno">  686</span>                 <span class="stringliteral">&quot;Handle points to SHM-offset [&quot;</span> &lt;&lt; offset_from_pool_base &lt;&lt; <span class="stringliteral">&quot;] (serialized).  Serialized contents are &quot;</span></div>
<div class="line"><a id="l00687" name="l00687"></a><span class="lineno">  687</span>                 <span class="stringliteral">&quot;[&quot;</span> &lt;&lt; buffers_dump_string(serialization.const_buffer(), <span class="stringliteral">&quot;  &quot;</span>) &lt;&lt; <span class="stringliteral">&quot;].&quot;</span>);</div>
<div class="line"><a id="l00688" name="l00688"></a><span class="lineno">  688</span> </div>
<div class="line"><a id="l00689" name="l00689"></a><span class="lineno">  689</span>  <span class="keywordflow">return</span> serialization;</div>
<div class="line"><a id="l00690" name="l00690"></a><span class="lineno">  690</span>} <span class="comment">// Pool_arena::lend_object()</span></div>
<div class="line"><a id="l00691" name="l00691"></a><span class="lineno">  691</span> </div>
<div class="line"><a id="l00692" name="l00692"></a><span class="lineno">  692</span><span class="keyword">template</span>&lt;<span class="keyword">typename</span> T&gt;</div>
<div class="line"><a id="l00693" name="l00693"></a><span class="lineno"><a class="line" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#ad2f2b767d7da42e7e57592cc029386e5">  693</a></span><a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a662a55c9ba6eb5c389ddf9780ee801cb">Pool_arena::Handle&lt;T&gt;</a> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#ad2f2b767d7da42e7e57592cc029386e5">Pool_arena::borrow_object</a>(<span class="keyword">const</span> <a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a72867ce6e363dbc1ab1666768d8a7a09">Blob</a>&amp; serialization)</div>
<div class="line"><a id="l00694" name="l00694"></a><span class="lineno">  694</span>{</div>
<div class="line"><a id="l00695" name="l00695"></a><span class="lineno">  695</span>  <span class="keyword">using </span>Value = T;</div>
<div class="line"><a id="l00696" name="l00696"></a><span class="lineno">  696</span>  <span class="keyword">using </span>Shm_handle = <a class="code hl_struct" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html">Handle_in_shm&lt;Value&gt;</a>;</div>
<div class="line"><a id="l00697" name="l00697"></a><span class="lineno">  697</span>  <span class="keyword">using </span>flow::util::buffers_dump_string;</div>
<div class="line"><a id="l00698" name="l00698"></a><span class="lineno">  698</span>  <span class="keyword">using </span>boost::shared_ptr;</div>
<div class="line"><a id="l00699" name="l00699"></a><span class="lineno">  699</span> </div>
<div class="line"><a id="l00700" name="l00700"></a><span class="lineno">  700</span>  <span class="keywordflow">if</span> (!<a class="code hl_variable" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a308351dc72f76407cf845af163fa0124">m_pool</a>)</div>
<div class="line"><a id="l00701" name="l00701"></a><span class="lineno">  701</span>  {</div>
<div class="line"><a id="l00702" name="l00702"></a><span class="lineno">  702</span>    <span class="keywordflow">return</span> <a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a662a55c9ba6eb5c389ddf9780ee801cb">Handle&lt;Value&gt;</a>{};</div>
<div class="line"><a id="l00703" name="l00703"></a><span class="lineno">  703</span>  }</div>
<div class="line"><a id="l00704" name="l00704"></a><span class="lineno">  704</span>  <span class="comment">// else</span></div>
<div class="line"><a id="l00705" name="l00705"></a><span class="lineno">  705</span> </div>
<div class="line"><a id="l00706" name="l00706"></a><span class="lineno">  706</span>  ptrdiff_t offset_from_pool_base;</div>
<div class="line"><a id="l00707" name="l00707"></a><span class="lineno">  707</span>  assert((serialization.size() == <span class="keyword">sizeof</span>(offset_from_pool_base))</div>
<div class="line"><a id="l00708" name="l00708"></a><span class="lineno">  708</span>         &amp;&amp; <span class="stringliteral">&quot;lend_object() and borrow_object() incompatible?  Bug?&quot;</span>);</div>
<div class="line"><a id="l00709" name="l00709"></a><span class="lineno">  709</span> </div>
<div class="line"><a id="l00710" name="l00710"></a><span class="lineno">  710</span>  offset_from_pool_base = *(<span class="keyword">reinterpret_cast&lt;</span>decltype(offset_from_pool_base) <span class="keyword">const </span>*<span class="keyword">&gt;</span></div>
<div class="line"><a id="l00711" name="l00711"></a><span class="lineno">  711</span>                              (serialization.const_data()));</div>
<div class="line"><a id="l00712" name="l00712"></a><span class="lineno">  712</span>  <span class="keyword">const</span> <span class="keyword">auto</span> handle_state</div>
<div class="line"><a id="l00713" name="l00713"></a><span class="lineno">  713</span>    = <span class="keyword">reinterpret_cast&lt;</span>Shm_handle*<span class="keyword">&gt;</span></div>
<div class="line"><a id="l00714" name="l00714"></a><span class="lineno">  714</span>        (<span class="keyword">static_cast&lt;</span>uint8_t*<span class="keyword">&gt;</span>(<a class="code hl_variable" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a308351dc72f76407cf845af163fa0124">m_pool</a>-&gt;get_address()) + offset_from_pool_base);</div>
<div class="line"><a id="l00715" name="l00715"></a><span class="lineno">  715</span> </div>
<div class="line"><a id="l00716" name="l00716"></a><span class="lineno">  716</span>  <span class="comment">// Now simply do just as in construct():</span></div>
<div class="line"><a id="l00717" name="l00717"></a><span class="lineno">  717</span> </div>
<div class="line"><a id="l00718" name="l00718"></a><span class="lineno">  718</span>  shared_ptr&lt;Shm_handle&gt; real_shm_handle{handle_state, [<span class="keyword">this</span>](Shm_handle* handle_state)</div>
<div class="line"><a id="l00719" name="l00719"></a><span class="lineno">  719</span>  {</div>
<div class="line"><a id="l00720" name="l00720"></a><span class="lineno">  720</span>    handle_deleter_impl&lt;Value&gt;(handle_state);</div>
<div class="line"><a id="l00721" name="l00721"></a><span class="lineno">  721</span>  }};</div>
<div class="line"><a id="l00722" name="l00722"></a><span class="lineno">  722</span> </div>
<div class="line"><a id="l00723" name="l00723"></a><span class="lineno">  723</span>  FLOW_LOG_TRACE(<span class="stringliteral">&quot;SHM-classic pool [&quot;</span> &lt;&lt; *<span class="keyword">this</span> &lt;&lt; <span class="stringliteral">&quot;]: Deserialized SHM outer handle [&quot;</span> &lt;&lt; real_shm_handle &lt;&lt; <span class="stringliteral">&quot;] &quot;</span></div>
<div class="line"><a id="l00724" name="l00724"></a><span class="lineno">  724</span>                 <span class="stringliteral">&quot;(type [&quot;</span> &lt;&lt; <span class="keyword">typeid</span>(Value).name() &lt;&lt; <span class="stringliteral">&quot;]) &quot;</span></div>
<div class="line"><a id="l00725" name="l00725"></a><span class="lineno">  725</span>                 <span class="stringliteral">&quot;after IPC-receipt: Owner-count is at [&quot;</span> &lt;&lt; handle_state-&gt;m_atomic_owner_ct &lt;&lt; <span class="stringliteral">&quot;] &quot;</span></div>
<div class="line"><a id="l00726" name="l00726"></a><span class="lineno">  726</span>                 <span class="stringliteral">&quot;(may change concurrently; but includes us at least hence must be 1+).  &quot;</span></div>
<div class="line"><a id="l00727" name="l00727"></a><span class="lineno">  727</span>                 <span class="stringliteral">&quot;Handle points to SHM-offset [&quot;</span> &lt;&lt; offset_from_pool_base &lt;&lt; <span class="stringliteral">&quot;] (deserialized).  Serialized &quot;</span></div>
<div class="line"><a id="l00728" name="l00728"></a><span class="lineno">  728</span>                 <span class="stringliteral">&quot;contents are [&quot;</span> &lt;&lt; buffers_dump_string(serialization.const_buffer(), <span class="stringliteral">&quot;  &quot;</span>) &lt;&lt; <span class="stringliteral">&quot;].&quot;</span>);</div>
<div class="line"><a id="l00729" name="l00729"></a><span class="lineno">  729</span> </div>
<div class="line"><a id="l00730" name="l00730"></a><span class="lineno">  730</span>  <span class="keywordflow">return</span> <a class="code hl_typedef" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a662a55c9ba6eb5c389ddf9780ee801cb">Handle&lt;Value&gt;</a>{std::move(real_shm_handle), &amp;handle_state-&gt;m_obj};</div>
<div class="line"><a id="l00731" name="l00731"></a><span class="lineno">  731</span>} <span class="comment">// Pool_arena::borrow_object()</span></div>
<div class="line"><a id="l00732" name="l00732"></a><span class="lineno">  732</span> </div>
<div class="line"><a id="l00733" name="l00733"></a><span class="lineno">  733</span><span class="keyword">template</span>&lt;<span class="keyword">typename</span> T&gt;</div>
<div class="line"><a id="l00734" name="l00734"></a><span class="lineno"><a class="line" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#ade690ffcab383978303f974e889deb54">  734</a></span><span class="keywordtype">void</span> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#ade690ffcab383978303f974e889deb54">Pool_arena::handle_deleter_impl</a>(<a class="code hl_struct" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html">Handle_in_shm&lt;T&gt;</a>* handle_state)</div>
<div class="line"><a id="l00735" name="l00735"></a><span class="lineno">  735</span>{</div>
<div class="line"><a id="l00736" name="l00736"></a><span class="lineno">  736</span>  <span class="keyword">using </span>Value = T;</div>
<div class="line"><a id="l00737" name="l00737"></a><span class="lineno">  737</span>  <span class="keyword">using </span>Atomic_owner_ct = <span class="keyword">typename</span> <a class="code hl_typedef" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html#aef706713d40d801d0cb213e08201c571">Handle_in_shm&lt;Value&gt;::Atomic_owner_ct</a>;</div>
<div class="line"><a id="l00738" name="l00738"></a><span class="lineno">  738</span> </div>
<div class="line"><a id="l00739" name="l00739"></a><span class="lineno">  739</span>  <span class="keyword">const</span> <span class="keyword">auto</span> prev_owner_ct = handle_state-&gt;<a class="code hl_variable" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html#aa801c3aa3c8f15945c5ac94936bd072d">m_atomic_owner_ct</a>--;</div>
<div class="line"><a id="l00740" name="l00740"></a><span class="lineno">  740</span>  <span class="comment">// Post-op form to avoid underflow for sure, for this assert():</span></div>
<div class="line"><a id="l00741" name="l00741"></a><span class="lineno">  741</span>  assert((prev_owner_ct != 0) &amp;&amp; <span class="stringliteral">&quot;How was owner_ct=0, yet handle was still alive?  Bug?&quot;</span>);</div>
<div class="line"><a id="l00742" name="l00742"></a><span class="lineno">  742</span> </div>
<div class="line"><a id="l00743" name="l00743"></a><span class="lineno">  743</span>  FLOW_LOG_TRACE(<span class="stringliteral">&quot;SHM-classic pool [&quot;</span> &lt;&lt; *<span class="keyword">this</span> &lt;&lt; <span class="stringliteral">&quot;]: Return SHM outer handle [&quot;</span> &lt;&lt; handle_state &lt;&lt; <span class="stringliteral">&quot;] &quot;</span></div>
<div class="line"><a id="l00744" name="l00744"></a><span class="lineno">  744</span>                 <span class="stringliteral">&quot;(type [&quot;</span> &lt;&lt; <span class="keyword">typeid</span>(Value).name() &lt;&lt; <span class="stringliteral">&quot;]) &quot;</span></div>
<div class="line"><a id="l00745" name="l00745"></a><span class="lineno">  745</span>                 <span class="stringliteral">&quot;because, for a given owner, a Handle is being destroyed due to shared_ptr ref-count reaching 0: &quot;</span></div>
<div class="line"><a id="l00746" name="l00746"></a><span class="lineno">  746</span>                 <span class="stringliteral">&quot;Owner-count decremented to [&quot;</span> &lt;&lt; (prev_owner_ct - 1) &lt;&lt; <span class="stringliteral">&quot;] (may change concurrently &quot;</span></div>
<div class="line"><a id="l00747" name="l00747"></a><span class="lineno">  747</span>                 <span class="stringliteral">&quot;unless 0).  If it is 0 now, shall invoke dtor and SHM-dealloc now.&quot;</span>);</div>
<div class="line"><a id="l00748" name="l00748"></a><span class="lineno">  748</span>  <span class="keywordflow">if</span> (prev_owner_ct == 1)</div>
<div class="line"><a id="l00749" name="l00749"></a><span class="lineno">  749</span>  {</div>
<div class="line"><a id="l00750" name="l00750"></a><span class="lineno">  750</span>    <span class="comment">// Now it is zero.  Time to destroy the whole thing; yay!  Execute the reverse (order) of construct&lt;&gt;() logic.</span></div>
<div class="line"><a id="l00751" name="l00751"></a><span class="lineno">  751</span>    {</div>
<div class="line"><a id="l00752" name="l00752"></a><span class="lineno">  752</span>      <span class="comment">/* As promised, and rather crucically, help out by setting this context (same as we had around ctor --</span></div>
<div class="line"><a id="l00753" name="l00753"></a><span class="lineno">  753</span><span class="comment">       * but this time it&#39;s more essential, since they can pretty easily do it themselves when constructing; but</span></div>
<div class="line"><a id="l00754" name="l00754"></a><span class="lineno">  754</span><span class="comment">       * doing it at the time of reaching shared_ptr ref-count=0... that&#39;s a tall order). */</span></div>
<div class="line"><a id="l00755" name="l00755"></a><span class="lineno">  755</span>      <a class="code hl_class" href="classipc_1_1shm_1_1stl_1_1Arena__activator.html">Pool_arena_activator</a> ctx{<span class="keyword">this</span>};</div>
<div class="line"><a id="l00756" name="l00756"></a><span class="lineno">  756</span> </div>
<div class="line"><a id="l00757" name="l00757"></a><span class="lineno">  757</span>      <span class="comment">// But regardless:</span></div>
<div class="line"><a id="l00758" name="l00758"></a><span class="lineno">  758</span>      (handle_state-&gt;<a class="code hl_variable" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html#ac787f6c20943bc76027cf25c7548d797">m_obj</a>).~Value();</div>
<div class="line"><a id="l00759" name="l00759"></a><span class="lineno">  759</span>    }</div>
<div class="line"><a id="l00760" name="l00760"></a><span class="lineno">  760</span>    (handle_state-&gt;<a class="code hl_variable" href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html#aa801c3aa3c8f15945c5ac94936bd072d">m_atomic_owner_ct</a>).~Atomic_owner_ct();</div>
<div class="line"><a id="l00761" name="l00761"></a><span class="lineno">  761</span> </div>
<div class="line"><a id="l00762" name="l00762"></a><span class="lineno">  762</span>    <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a394973b7cfb67b67113043810804337d">deallocate</a>(<span class="keyword">static_cast&lt;</span><span class="keywordtype">void</span>*<span class="keyword">&gt;</span>(handle_state));</div>
<div class="line"><a id="l00763" name="l00763"></a><span class="lineno">  763</span>  }</div>
<div class="line"><a id="l00764" name="l00764"></a><span class="lineno">  764</span>  <span class="comment">// else if (prev_owner_ct &gt; 1) { It is now 1+; stays alive.  Done for now. }</span></div>
<div class="line"><a id="l00765" name="l00765"></a><span class="lineno">  765</span>} <span class="comment">// Pool_arena::handle_deleter_impl()</span></div>
<div class="line"><a id="l00766" name="l00766"></a><span class="lineno">  766</span> </div>
<div class="line"><a id="l00767" name="l00767"></a><span class="lineno">  767</span><span class="keyword">template</span>&lt;<span class="keyword">typename</span> T, <span class="keyword">typename</span>... Ctor_args&gt;</div>
<div class="line"><a id="l00768" name="l00768"></a><span class="lineno"><a class="line" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a2823d6522e276e7b7b5bd518327b85d6">  768</a></span><span class="keywordtype">void</span> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a2823d6522e276e7b7b5bd518327b85d6">Pool_arena::construct_at</a>(T* obj, Ctor_args&amp;&amp;... ctor_args)</div>
<div class="line"><a id="l00769" name="l00769"></a><span class="lineno">  769</span>{</div>
<div class="line"><a id="l00770" name="l00770"></a><span class="lineno">  770</span>  <span class="keyword">using </span>Value = T;</div>
<div class="line"><a id="l00771" name="l00771"></a><span class="lineno">  771</span> </div>
<div class="line"><a id="l00772" name="l00772"></a><span class="lineno">  772</span>  <span class="comment">// Use placement-new expression used by C++20&#39;s construct_at() per cppreference.com.</span></div>
<div class="line"><a id="l00773" name="l00773"></a><span class="lineno">  773</span>  ::new (<span class="keyword">const_cast&lt;</span><span class="keywordtype">void</span>*<span class="keyword">&gt;</span></div>
<div class="line"><a id="l00774" name="l00774"></a><span class="lineno">  774</span>           (<span class="keyword">static_cast&lt;</span><span class="keywordtype">void</span> <span class="keyword">const </span><span class="keyword">volatile </span>*<span class="keyword">&gt;</span></div>
<div class="line"><a id="l00775" name="l00775"></a><span class="lineno">  775</span>              (obj)))</div>
<div class="line"><a id="l00776" name="l00776"></a><span class="lineno">  776</span>    Value(std::forward&lt;Ctor_args&gt;(ctor_args)...);</div>
<div class="line"><a id="l00777" name="l00777"></a><span class="lineno">  777</span>}</div>
<div class="line"><a id="l00778" name="l00778"></a><span class="lineno">  778</span> </div>
<div class="line"><a id="l00779" name="l00779"></a><span class="lineno">  779</span><span class="keyword">template</span>&lt;<span class="keyword">typename</span> Handle_name_func&gt;</div>
<div class="line"><a id="l00780" name="l00780"></a><span class="lineno"><a class="line" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a9e720283945eefe3d941b185e95d2ce1">  780</a></span><span class="keywordtype">void</span> <a class="code hl_function" href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a9e720283945eefe3d941b185e95d2ce1">Pool_arena::for_each_persistent</a>(<span class="keyword">const</span> Handle_name_func&amp; handle_name_func) <span class="comment">// Static.</span></div>
<div class="line"><a id="l00781" name="l00781"></a><span class="lineno">  781</span>{</div>
<div class="line"><a id="l00782" name="l00782"></a><span class="lineno">  782</span>  <a class="code hl_function" href="namespaceipc_1_1util.html#a74135195ff6c2f840092c21e522f964a">util::for_each_persistent_shm_pool</a>(handle_name_func);</div>
<div class="line"><a id="l00783" name="l00783"></a><span class="lineno">  783</span>  <span class="comment">// (See that guy&#39;s doc header for why we didn&#39;t just do what&#39;s necessary right in here.)</span></div>
<div class="line"><a id="l00784" name="l00784"></a><span class="lineno">  784</span>}</div>
<div class="line"><a id="l00785" name="l00785"></a><span class="lineno">  785</span> </div>
<div class="line"><a id="l00786" name="l00786"></a><span class="lineno">  786</span>} <span class="comment">// namespace ipc::shm::classic</span></div>
<div class="ttc" id="aarena__activator_8hpp_html"><div class="ttname"><a href="arena__activator_8hpp.html">arena_activator.hpp</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html">ipc::shm::classic::Pool_arena</a></div><div class="ttdoc">A SHM-classic interface around a single SHM pool with allocation-algorithm services by boost....</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00150">pool_arena.hpp:153</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_a07fec7ff0ba494dca0f0a010270cc35f"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a07fec7ff0ba494dca0f0a010270cc35f">ipc::shm::classic::Pool_arena::Pointer</a></div><div class="ttdeci">::ipc::bipc::offset_ptr&lt; T &gt; Pointer</div><div class="ttdoc">SHM-storable fancy-pointer.</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00164">pool_arena.hpp:164</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_a2823d6522e276e7b7b5bd518327b85d6"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a2823d6522e276e7b7b5bd518327b85d6">ipc::shm::classic::Pool_arena::construct_at</a></div><div class="ttdeci">static void construct_at(T *obj, Ctor_args &amp;&amp;... ctor_args)</div><div class="ttdoc">std::construct_at() equivalent; unavailable until C++20, so here it is.</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00768">pool_arena.hpp:768</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_a308351dc72f76407cf845af163fa0124"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a308351dc72f76407cf845af163fa0124">ipc::shm::classic::Pool_arena::m_pool</a></div><div class="ttdeci">std::optional&lt; Pool &gt; m_pool</div><div class="ttdoc">Attached SHM pool. If ctor fails in non-throwing fashion then this remains null. Immutable after ctor...</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00614">pool_arena.hpp:614</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_a394973b7cfb67b67113043810804337d"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a394973b7cfb67b67113043810804337d">ipc::shm::classic::Pool_arena::deallocate</a></div><div class="ttdeci">bool deallocate(void *buf_not_null) noexcept</div><div class="ttdoc">Undoes effects of local allocate() that returned buf_not_null; or another-process's allocate() that r...</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8cpp_source.html#l00133">pool_arena.cpp:133</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_a5914c3039a00fa0396f34e9b357934a4"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a5914c3039a00fa0396f34e9b357934a4">ipc::shm::classic::Pool_arena::Pool</a></div><div class="ttdeci">::ipc::bipc::basic_managed_shared_memory&lt; char, ::ipc::bipc::rbtree_best_fit&lt;::ipc::bipc::mutex_family &gt;, ::ipc::bipc::null_index &gt; Pool</div><div class="ttdoc">The SHM pool type one instance of which is managed by *this.</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00509">pool_arena.hpp:511</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_a662a55c9ba6eb5c389ddf9780ee801cb"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a662a55c9ba6eb5c389ddf9780ee801cb">ipc::shm::classic::Pool_arena::Handle</a></div><div class="ttdeci">boost::shared_ptr&lt; T &gt; Handle</div><div class="ttdoc">Outer handle to a SHM-stored object; really a regular-looking shared_ptr but with custom deleter that...</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00188">pool_arena.hpp:188</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_a71009bb725b4cd68bea4ac99fa81ee2e"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a71009bb725b4cd68bea4ac99fa81ee2e">ipc::shm::classic::Pool_arena::m_pool_name</a></div><div class="ttdeci">const Shared_name m_pool_name</div><div class="ttdoc">SHM pool name as set immutably at construction.</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00493">pool_arena.hpp:493</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_a72867ce6e363dbc1ab1666768d8a7a09"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a72867ce6e363dbc1ab1666768d8a7a09">ipc::shm::classic::Pool_arena::Blob</a></div><div class="ttdeci">flow::util::Blob_sans_log_context Blob</div><div class="ttdoc">Alias for a light-weight blob.</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00194">pool_arena.hpp:194</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_a77acacecacdd45514ebf9db99b4ab4c3"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a77acacecacdd45514ebf9db99b4ab4c3">ipc::shm::classic::Pool_arena::Pool_arena</a></div><div class="ttdeci">Pool_arena(flow::log::Logger *logger_ptr, const Shared_name &amp;pool_name, util::Create_only mode_tag, size_t pool_sz, const util::Permissions &amp;perms=util::Permissions{}, Error_code *err_code=nullptr)</div><div class="ttdoc">Construct Pool_arena accessor object to non-existing named SHM pool, creating it first.</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8cpp_source.html#l00060">pool_arena.cpp:60</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_a9487dcff44fde9a2c12d64b51c16c85e"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a9487dcff44fde9a2c12d64b51c16c85e">ipc::shm::classic::Pool_arena::remove_persistent</a></div><div class="ttdeci">static void remove_persistent(flow::log::Logger *logger_ptr, const Shared_name &amp;name, Error_code *err_code=nullptr)</div><div class="ttdoc">Removes the named SHM pool object.</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8cpp_source.html#l00165">pool_arena.cpp:165</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_a9da3a100a0b7199644edbadacc9083c9"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a9da3a100a0b7199644edbadacc9083c9">ipc::shm::classic::Pool_arena::allocate</a></div><div class="ttdeci">void * allocate(size_t n)</div><div class="ttdoc">Allocates buffer of specified size, in bytes, in the accessed pool; returns locally-derefernceable ad...</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8cpp_source.html#l00103">pool_arena.cpp:103</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_a9e720283945eefe3d941b185e95d2ce1"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#a9e720283945eefe3d941b185e95d2ce1">ipc::shm::classic::Pool_arena::for_each_persistent</a></div><div class="ttdeci">static void for_each_persistent(const Handle_name_func &amp;handle_name_func)</div><div class="ttdoc">Lists all named SHM pool objects currently persisting, invoking the given handler synchronously on ea...</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00780">pool_arena.hpp:780</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_ab9f7ea056a55183d00dcbce573afcf36"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#ab9f7ea056a55183d00dcbce573afcf36">ipc::shm::classic::Pool_arena::construct</a></div><div class="ttdeci">Handle&lt; T &gt; construct(Ctor_args &amp;&amp;... ctor_args)</div><div class="ttdoc">Constructs an object of given type with given ctor args, having allocated space directly in attached ...</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00630">pool_arena.hpp:630</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_aca8bf9fe738df70fd502111330089c90"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#aca8bf9fe738df70fd502111330089c90">ipc::shm::classic::Pool_arena::~Pool_arena</a></div><div class="ttdeci">~Pool_arena()</div><div class="ttdoc">Destroys Pool_arena accessor object.</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8cpp_source.html#l00098">pool_arena.cpp:98</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_acb300e64f92ab0aa5b70f8313c79a899"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#acb300e64f92ab0aa5b70f8313c79a899">ipc::shm::classic::Pool_arena::lend_object</a></div><div class="ttdeci">Blob lend_object(const Handle&lt; T &gt; &amp;handle)</div><div class="ttdoc">Adds an owner process to the owner count of the given construct()-created handle, and returns an opaq...</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00661">pool_arena.hpp:661</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_ad2d54cc87b56613bba32aabd2c52ef13"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#ad2d54cc87b56613bba32aabd2c52ef13">ipc::shm::classic::Pool_arena::is_handle_in_arena</a></div><div class="ttdeci">bool is_handle_in_arena(const Handle&lt; T &gt; &amp;handle) const</div><div class="ttdoc">Returns true if and only if handle came from either this-&gt;construct&lt;T&gt;() or this-&gt;borrow_object&lt;T&gt;().</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00622">pool_arena.hpp:622</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_ad2f2b767d7da42e7e57592cc029386e5"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#ad2f2b767d7da42e7e57592cc029386e5">ipc::shm::classic::Pool_arena::borrow_object</a></div><div class="ttdeci">Handle&lt; T &gt; borrow_object(const Blob &amp;serialization)</div><div class="ttdoc">Completes the cross-process operation begun by lend_object() that returned serialization; to be invok...</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00693">pool_arena.hpp:693</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1classic_1_1Pool__arena_html_ade690ffcab383978303f974e889deb54"><div class="ttname"><a href="classipc_1_1shm_1_1classic_1_1Pool__arena.html#ade690ffcab383978303f974e889deb54">ipc::shm::classic::Pool_arena::handle_deleter_impl</a></div><div class="ttdeci">void handle_deleter_impl(Handle_in_shm&lt; T &gt; *handle_state)</div><div class="ttdoc">Identical deleter for Handle returned by both construct() and borrow_object(); invoked when a given p...</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00734">pool_arena.hpp:734</a></div></div>
<div class="ttc" id="aclassipc_1_1shm_1_1stl_1_1Arena__activator_html"><div class="ttname"><a href="classipc_1_1shm_1_1stl_1_1Arena__activator.html">ipc::shm::stl::Arena_activator</a></div><div class="ttdoc">RAII-style class operating a stack-like notion of a the given thread's currently active SHM-aware Are...</div><div class="ttdef"><b>Definition:</b> <a href="arena__activator_8hpp_source.html#l00040">arena_activator.hpp:41</a></div></div>
<div class="ttc" id="aclassipc_1_1util_1_1Shared__name_html"><div class="ttname"><a href="classipc_1_1util_1_1Shared__name.html">ipc::util::Shared_name</a></div><div class="ttdoc">String-wrapping abstraction representing a name uniquely distinguishing a kernel-persistent entity fr...</div><div class="ttdef"><b>Definition:</b> <a href="shared__name_8hpp_source.html#l00241">shared_name.hpp:242</a></div></div>
<div class="ttc" id="anamespaceipc_1_1shm_1_1classic_html"><div class="ttname"><a href="namespaceipc_1_1shm_1_1classic.html">ipc::shm::classic</a></div><div class="ttdoc">ipc::shm sub-module with the SHM-classic SHM-provider. See ipc::shm doc header for introduction.</div><div class="ttdef"><b>Definition:</b> <a href="shm_2classic_2classic__fwd_8hpp_source.html#l00025">classic_fwd.hpp:26</a></div></div>
<div class="ttc" id="anamespaceipc_1_1shm_1_1classic_html_ac0a52218467710995cc6c74538be6012"><div class="ttname"><a href="namespaceipc_1_1shm_1_1classic.html#ac0a52218467710995cc6c74538be6012">ipc::shm::classic::Shared_name</a></div><div class="ttdeci">util::Shared_name Shared_name</div><div class="ttdoc">Short-hand for util::Shared_name; used in particular for SHM pool names at least.</div><div class="ttdef"><b>Definition:</b> <a href="shm_2classic_2classic__fwd_8hpp_source.html#l00048">classic_fwd.hpp:48</a></div></div>
<div class="ttc" id="anamespaceipc_1_1util_html_a1b398ae730d1e6040687cb2397115152"><div class="ttname"><a href="namespaceipc_1_1util.html#a1b398ae730d1e6040687cb2397115152">ipc::util::Permissions</a></div><div class="ttdeci">bipc::permissions Permissions</div><div class="ttdoc">Short-hand for Unix (POSIX) permissions class.</div><div class="ttdef"><b>Definition:</b> <a href="util__fwd_8hpp_source.html#l00161">util_fwd.hpp:161</a></div></div>
<div class="ttc" id="anamespaceipc_1_1util_html_a3e03491b5b2b5fac26551a220946d6e5"><div class="ttname"><a href="namespaceipc_1_1util.html#a3e03491b5b2b5fac26551a220946d6e5">ipc::util::Open_only</a></div><div class="ttdeci">bipc::open_only_t Open_only</div><div class="ttdoc">Tag type indicating an ideally-atomic open-if-exists-else-fail operation.</div><div class="ttdef"><b>Definition:</b> <a href="util__fwd_8hpp_source.html#l00155">util_fwd.hpp:155</a></div></div>
<div class="ttc" id="anamespaceipc_1_1util_html_a74135195ff6c2f840092c21e522f964a"><div class="ttname"><a href="namespaceipc_1_1util.html#a74135195ff6c2f840092c21e522f964a">ipc::util::for_each_persistent_shm_pool</a></div><div class="ttdeci">void for_each_persistent_shm_pool(const Handle_name_func &amp;handle_name_func)</div><div class="ttdoc">Equivalent to shm::classic::Pool_arena::for_each_persistent().</div><div class="ttdef"><b>Definition:</b> <a href="util_8hpp_source.html#l00131">util.hpp:131</a></div></div>
<div class="ttc" id="anamespaceipc_1_1util_html_a9571de958538d7a4a8649bbfecfac0b9"><div class="ttname"><a href="namespaceipc_1_1util.html#a9571de958538d7a4a8649bbfecfac0b9">ipc::util::Open_or_create</a></div><div class="ttdeci">bipc::open_or_create_t Open_or_create</div><div class="ttdoc">Tag type indicating an atomic open-if-exists-else-create operation.</div><div class="ttdef"><b>Definition:</b> <a href="util__fwd_8hpp_source.html#l00152">util_fwd.hpp:152</a></div></div>
<div class="ttc" id="anamespaceipc_1_1util_html_a9d84c2bab504e6de32b20c77ca9723a2"><div class="ttname"><a href="namespaceipc_1_1util.html#a9d84c2bab504e6de32b20c77ca9723a2">ipc::util::Create_only</a></div><div class="ttdeci">bipc::create_only_t Create_only</div><div class="ttdoc">Tag type indicating a create-unless-exists-else-fail operation.</div><div class="ttdef"><b>Definition:</b> <a href="util__fwd_8hpp_source.html#l00158">util_fwd.hpp:158</a></div></div>
<div class="ttc" id="anamespaceipc_1_1util_html_ae0be7edba7e30ffa3f8b742af621f2ab"><div class="ttname"><a href="namespaceipc_1_1util.html#ae0be7edba7e30ffa3f8b742af621f2ab">ipc::util::Blob_const</a></div><div class="ttdeci">boost::asio::const_buffer Blob_const</div><div class="ttdoc">Short-hand for an immutable blob somewhere in memory, stored as exactly a void const * and a size_t.</div><div class="ttdef"><b>Definition:</b> <a href="util__fwd_8hpp_source.html#l00134">util_fwd.hpp:134</a></div></div>
<div class="ttc" id="anamespaceipc_html_aa3192e586cc45d3e7c22463bf2760f89"><div class="ttname"><a href="namespaceipc.html#aa3192e586cc45d3e7c22463bf2760f89">ipc::Error_code</a></div><div class="ttdeci">flow::Error_code Error_code</div><div class="ttdoc">Short-hand for flow::Error_code which is very common.</div><div class="ttdef"><b>Definition:</b> <a href="common_8hpp_source.html#l00298">common.hpp:298</a></div></div>
<div class="ttc" id="ashared__name_8hpp_html"><div class="ttname"><a href="shared__name_8hpp.html">shared_name.hpp</a></div></div>
<div class="ttc" id="ashm_2classic_2classic__fwd_8hpp_html"><div class="ttname"><a href="shm_2classic_2classic__fwd_8hpp.html">classic_fwd.hpp</a></div></div>
<div class="ttc" id="astructipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm_html"><div class="ttname"><a href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html">ipc::shm::classic::Pool_arena::Handle_in_shm</a></div><div class="ttdoc">The data structure stored in SHM corresponding to an original construct()-returned Handle; exactly on...</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00525">pool_arena.hpp:526</a></div></div>
<div class="ttc" id="astructipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm_html_aa801c3aa3c8f15945c5ac94936bd072d"><div class="ttname"><a href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html#aa801c3aa3c8f15945c5ac94936bd072d">ipc::shm::classic::Pool_arena::Handle_in_shm::m_atomic_owner_ct</a></div><div class="ttdeci">Atomic_owner_ct m_atomic_owner_ct</div><div class="ttdoc">See Atomic_owner_ct doc header. This value is 1+; once it reaches 0 *this is destroyed in SHM.</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00549">pool_arena.hpp:549</a></div></div>
<div class="ttc" id="astructipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm_html_ac787f6c20943bc76027cf25c7548d797"><div class="ttname"><a href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html#ac787f6c20943bc76027cf25c7548d797">ipc::shm::classic::Pool_arena::Handle_in_shm::m_obj</a></div><div class="ttdeci">T m_obj</div><div class="ttdoc">The constructed object; Handle::get() returns &amp;m_obj.</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00546">pool_arena.hpp:546</a></div></div>
<div class="ttc" id="astructipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm_html_aef706713d40d801d0cb213e08201c571"><div class="ttname"><a href="structipc_1_1shm_1_1classic_1_1Pool__arena_1_1Handle__in__shm.html#aef706713d40d801d0cb213e08201c571">ipc::shm::classic::Pool_arena::Handle_in_shm::Atomic_owner_ct</a></div><div class="ttdeci">std::atomic&lt; unsigned int &gt; Atomic_owner_ct</div><div class="ttdoc">Atomically accessed count of each time the following events occurs for a given Handle_in_shm in the b...</div><div class="ttdef"><b>Definition:</b> <a href="pool__arena_8hpp_source.html#l00537">pool_arena.hpp:537</a></div></div>
<div class="ttc" id="autil_8hpp_html"><div class="ttname"><a href="util_8hpp.html">util.hpp</a></div></div>
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